TREATMENT OF ACIDIC RAW WATER USING LIMESTONE
NADIAH BINTI MOKHTAR
A project report submitted in partial fulfillment of the requirements for the award of the degree of Master of Engineering
(Civil - Wastewater)
Faculty of Civil Engineering
Universiti Teknologi Malaysia
NOVEMBER 2006

To my beloved abah and mak;
Tuan Haji Mokhtar Omar & Pn Hjh Jasnin Abd Malek, iii

iv
ACKNOWLEDGMENT
I would like to express my gratefulness to Allah S.W.T for giving me strength and wisdom in my project work. In preparing this thesis, I was in contact with many people, researchers, academicians and technicians. They all have contributed to my understanding and valuable thoughts during my project.
First and foremost, I wish to express my sincere appreciation to my project supervisor, Dr. Azmi Aris, for encouragement, guidance and critics. His ideas enlighten my curiosity. Without his continued support and interest, this thesis would not have been the same as presented here.
My fellow postgraduate students, Ain and Kam should also be recognized for their support. My sincere appreciation also extends to all SAJ members, En. Aliman and Pn. Fadzlin and not forgotten Environmental Laboratory technicians, Pak Usop,
En. Ramli and En. Muzaffar who have provided assistance at various occasions.
Their views and tips are useful indeed. Unfortunately, it is not possible to list all of them in this limited space.

v
ABSTRACT
Sg. River is the only raw water source for Yong Peng 2 and 3 treatment plants which supply treated water for domestic, institutional, commercial and industrial use in Batu Pahat. Between the months of January to May 2005, Sg.
Bekok registered a low pH of between 2.89 – 3.06. The acidic water hence, escalated the cost for water treatment in Yong Peng. (Southern Water Corporation
Sdn. Bhd., 1999). In several extreme cases, the plants were incapable to supply sufficient water to the consumers in Batu Pahat area. The present study attempts to investigate the viability of limestone in treating acidic raw water with high concentration of iron and manganese. Sample of water was collected from tributary of Parit Ngamarto, Bekok Intake and Semberong Lagoon. A lab-scale study using plug-flow reactor system that consists of four limestone-drains was used to treat the raw water. The pH reading was monitored at inflow, outflow and three intermediate points within limestone reactor while effluent was collected for Fe and Mn analysis.
Parit Ngamarto, Bekok Intake and Semberong Lagoon raw water sample was recorded an initial pH of 2.5, 2.89 and 3.12 with acidity of 530 mg/L as CaCO
3,
75 mg/L as CaCO
3 and 51mg/L as CaCO
3
, respectively. The pH rise gradually as the water flow through limestone-drain at different flow rates (88 mL/min, 42 mL/min and 21 mL/min). The rate of pH rise varies depending on the acidity of the water.
The rise of pH was also affected by the amount of limestone used. As pH increased,
Fe and Mn concentration was found to decrease. By using statistical analysis i.e
Analysis of Variance (ANOVA), a significant increase in pH could be related to the quantity of the limestone used, acidity and flow rate (contact time).

vi
ABSTRAK
Sungai Bekok merupakan satu-satunya sumber air bagi Loji Rawatan Air
Yong Peng 2 dan 3 yang membekalkan air terawat untuk kegunaan domestik, institusi, komersil dan peindustrian di Batu Pahat. Di antara bulan Januari 2004 hingga Mei 2005, Sungai Bekok telah mencatatkan bacaan pH yang rendah di antara
2.89 – 3.06. Keadaan air yang menjadi terlalu berasid ini seterusnya meningkatkan kos rawatan air di Yong Peng (Southern Water Corporation Sdn. Bhd., 1999). Kos meneutralkan air telah meningkat dan penjadualan rawatan menjadi bertambah rumit. Pada kes-kes tertentu, loji tersebut tidak mampu menyediakan air mengikut keperluan penduduk. Kajian ini dijalankan bagi mengkaji keupayaan batu kapur dalam merawat air mentah yang berasid dengan kepekatan unsur Besi dan Mangan yang tinggi. Sampel air diambil dari anak Parit Ngamarto, Intake Bekok dan lagun
Semberong. Ujikaji makmal menggunakan sistem reaktor yang mengandungi empat parit yang dipenuhi dengan batu kapur digunakan untuk merawat air mentah.
Bacaan pH dipantau pada salur masuk, salur keluar dan tiga titik pemantauan di dalam reaktor. Efluen dikumpulkan untuk analisis unsur Fe dan Mn. Air mentah dari anak Parit Ngamarto, Intake Bekok dan lagun Semberong di rekodkan dengan pH awal 2.5, 2.89 dan 3.12 dan keasidan 530, 75 dan 51 mg/L CaCO
3
. Nilai pH di dapati meningkat secara perlahan-lahan apabila air mengalir melalui reaktor pada kadar alir yang berbeza (88 mL/min, 42 mL/min dan 21 mL/min). Kadar peningkatan pH meningkat secara berbeza bergantung kepada keasidan air. Apabila pH meningkat, kepekatan Fe dan Mn didapati menurun. Dengan menggunakan analisis statistik seperti Analysis of Variance (ANOVA), peningkatan pH dapat dikaitkan dengan kuantiti batu kapur yang digunakan, keasidan dan kadar alir (masa dedahan).

vii
TABLE OF CONTENTS
CHAPTER TITLE
DECLARATION
DEDICATION
ACKNOWLEDGEMENTS
ABSTRACT
ABSTRAK
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF SYMBOLS
LIST OF APPENDICES
I
II
INTRODUCTION
1.1
Preamble
1.2
Problem
1.3
Aim of Study
1.4
Study
1.5
Scope of Study
LITERATURE REVIEW
2.1
Water Catchment of Sg. Bekok
2.2
Theoretical background of acidic water development
1
4
4
1
3
5
6
7
7
PAGE vi vii x xi iv v ii iii xii xiv

III
IV
2.2.1 Peat soil
2.2.1.1Characteristic of peat soil
2.2.1.2Oxidation of pyrite
2.2.1.3Biological sulphur retention
2.2.2 Organic acid
2.3
Metal leaching
2.3.1 Ferum
2.3.2 Manganese
2.3.3 Aluminum
2.4
Limestone
2.4.1 Characteristic of limestone
2.4.2 Mechanism of pH adjustment
2.4.3 Previous study of limestone treatment
METHODOLOGY
3.1
Materials and equipments
3.2
Water quality analysis
3.2.1 Acidity measurement
3.2.2 Iron and Manganese
3.3
Experimental procedure
3.3.1
Batch-mode test
3.3.2
Continuous flow test
3.3.3
Aeration test
RESULTS AND DISCUSSIONS
4.1
Batch-mode study
4.2
Continuous flow study
4.2.1 pH
4.2.1.1 Parit Ngamarto tributary
4.2.1.2 Bekok Intake
31
31
32
33
34
36
22
24
24
25
26
26
27
29
14
15
15
16
16
18
11
12
13
13
8
9
7
7 viii
22

V
4.2.1.3 Semberong lagoon
4.2.2 Comparative analysis
4.2.3 Statistical analysis
4.2.4
Iron (Fe)
4.2.5
Manganese
4.3
Aeration
CONCLUSIONS AND RECOMMENDATIONS
5.1
Conclusions
5.2
Recommendations
REFERENCES
APPENDICES A - D
47
47
48
36
38
39
40
42
46
49
53 ix

x
LIST OF TABLES
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
TABLE NO.
2.1
2.2
3.1
3.2
4.1
4.2
TITLE PAGE
Effect of pH on the present of metal
Previous study on water/wastewater treatment using limestone
Characteristic of water sampling location
Reagent used in metal analysis
Characteristic of the raw water sample pH reading for Parit Ngamarto’s tributary at every sampling point pH reading for Bekok Intake at every sampling point pH reading for Semberong Lagoon at every sampling point
ANOVA for sample of Parit Ngamarto tributary
ANOVA for sample of Bekok Intake
ANOVA for sample of Semberong Lagoon
ANOVA for acidity
Fe removal at different contact time
Mn removal at different contact time
49
43
45
48
49
49
36
37
38
39
13
22
23
24

xi
LIST OF FIGURES
4.5
4.6
4.7
3.4
3.5
4.1
2.1
3.1
3.2
3.3
4.2
FIGURE NO.
1.1
4.3
4.4
4.8
4.9
TITLE
Population growth projections 1950-2025 (Data from
World Population prospect 1990,UN)
Simplified sulphur cycle in the soil
HACH DR/4000 Spectrophotometer
The set-up of batch mode test
The set-up of limestone-drain reactor
Continuous flow-mode test
Batch-mode treatment test conducted under aeration
Effect of limestone size on neutralizing acidic raw water
Profile of pH increase at different contact time for Parit
Ngamarto tributary water sample
Profile of pH increase at different contact time for Bekok
Intake water sample
Profile of pH increase at different contact time for
Semberong Lagoon water sample
Effect of acidity on pH adjustment
Armoring occur at the last limestone drain
Removal of iron in the water samples at different contact time
Removal of Mn in the water samples at different contact time
Effect of aeration to pH
PAGE
2
37
45
47
39
43
44
33
35
36
28
30
32
10
25
26
28

LIST OF SYMBOLS
Al t
Al o
Al i
-
-
-
Acid-mobilized Aluminum
Organic bound Aluminum
Dissolved inorganic Aluminum
Ca
2+
CaCO
3
-
Calcium ion
Calcium Carbonate
FeS
2
H
+
-
-
Pyrite
Hydrogen ion
H
2
O
HCO
3
-
M s of xii

t
R
Contact time
U b
Bulk density xiii

xiv
LIST OF APPENDICES
B
C
APPENDIX TITLE
A Experimental form for batch mode test
D
Experimental form for aeration test
Acidity data
Malaysia National Water Quality Standards (Revised
December 2004)
PAGE
53
54
55
58

CHAPTER I
INTRO N
1.1
Preamble
The importance of a dependable water supply has been recognized since ancient times. The digging of wells dates back to early Chinese and Egyptian history and aqueducts of the ancient Romans are considered today to be remarkable engineering achievement.
Water is a key component of socio-economic systems. It is the basis for agricultural, essential for many industries and for energy production. Its importance for human health and welfare is critical and thus supply of water for drinking and sanitation is of major concern everywhere.
The world of the late twentieth century is a place subject to many dynamic forces. Change is evidenced everywhere and in many different ways. Global population has expanded remarkably. Figure 1.1 shows the population growth projections between year 1950-2025 for Former USSF, Europe, America, Asia and
Africa. As the population expands and as living standards rise, albeit unequally in different parts of the world, so do the demands for increased exploitation of natural resources. Henceforth, water pollution increase as well as water demand rises for fulfilling living necessity.

Figure 1.1 Population growth projections 1950-2025 (Data from World population prospect 1990,UN.)
Between the years of 1900-1995, world population has increased two times meanwhile water demand increased by six times (WHO, 1993). Eventhough the total amount of water has finite limit, the freshwater portion is limited and contaminated by point and nonpoint sources. As this happen, many countries are rapidly reaching condition of water scarcity.
In Malaysia, water demand was expected to be around 3.8 bilion m
3
in 2000 as compared to 0.8 bilion m
3
in 1980 and 3.1m
3
in 1998 (Malaysia Water Industry
Guide 2001). While water is readily abundance in Malaysia, its quality is deteriorates due to human activities and partly, natural phenomena. .
2

3
1.2
Problem statement
Stream water contamination from non-point source is currently an important issue in river system management of agricultural area. The sources of the problem are normally due to the agricultural activities such as use of fertilizer and pesticide which eventually are carried away into the river by surface runoff.
Additionally, the water quality problem can also be attributed to the natural phenomena aggravated further by human activities such as those experienced at Sg.
Bekok, Batu Pahat. The Sg. Batu Pahat basin has a total catchment area of 1944 km
2
. It has two main tributaries, namely Sg. Simpang Kiri and Sg. Simpang Kanan.
Sg. Simpang Kanan is further subdivided into two main tributaries namely, Sg.
Bekok (catchment area 645 km
2
) and Sg. Semberong (catchment area 273 km
2
).
There are about four water treatment plants operating along Sg. Bekok.
Identified as among the raw water resources to the domestic water supply system in the Batu Pahat area, Sg. Bekok supply raw water directly to two water treatment plants, namely Yong Peng 2 and 3 Treatment Plant. Another two treatment plants, Sri Gading and Semberong Treatment Plant get raw water resources from an artificial lagoon which is also supplied by Sg. Bekok. The lagoon act as a reservoir and also for water quality stabilization before the water is pumped into the treatment plant. The Sg Bekok river basin is covering more than 100 km
2 area.
Sg. Bekok in recent years is facing severe water quality problem in term of pH. Between the months of January 2004 to May 2005, Sg. Bekok registered a low pH of between pH 2.89 – 3.06. The latest monitoring programme conducted by
Institute of Environmental and Water Resources Management (IPASA), between the months of February to May 2006 also confirmed the readings. This has caused operational problems to the water treatment plant that completely depending on the raw water supply from the Sg. Bekok. The acidic water has caused corrosion of plant turbine and pipeline. Burst of pipe line has occasionally been reported resulting in water supply disturbance and shortages. The cost to neutralise the water has also increased and treatment scheduling became more complicated. The high

4 level of acidity in the water has also resulted in higher metals content (Fe, Al and
Mn) concentrations, which exceeded the allowable limit set by the National
Standard for Drinking Water Quality.
Others factor to be considered causing pollution problem to Sg Bekok is point and nonpoint sources pollutant created by the land use development adjacent to the river. There are pollution point sources that obviously can be found along the river bank such as palm oil industry, paper mill industry and chicken farm. Besides, pollution non point sources such as sediments, pesticides and agricultural fertilizer and pathogens transported across the land surface by runoff and through the soil by percolating water can also be observed. These activities may also contribute to the presence of heavy metal in river water body.
The common method of neutralizing pH at the treatment plant is through the use of limes slurry. However, as the pH of the water is too low, the use of lime slurry has become too expensive. Use of limestone has been reported to be one of the cheap methods in neutralizing pH (Muslim, 2005). Thus, this study investigates the feasibility of limestone as an in-situ pH treatment.
1.3
To provide an alternative solution to the acidic water problem of Sg. Bekok, Batu
Pahat.
1.4
The objectives of the study are: i.
To determine the effectiveness of in-situ limestone treatment in adjusting the pH and reducing the acidity of the acidic raw water. ii.
To determine the minimum contact time required for the limestone process.

iii.
To explore the effect of limestone treatment on the removal of iron and manganese.
5
1.5
The study consists of a thorough experimental work using a laboratory scale plug flow reactor. The limestone is of about 30 mm diameter and is obtained locally. Actual raw water from Sg. Bekok is used in the experiment. The efficiency of treatment is evaluated based on pH adjustment and removal of iron and manganese.

CHAPTER II
LITERATURE REVIEW
Most of river systems are getting more complex due to multiple activities occurring in the catchment area. As such, surface water contamination problem caused by non-point sources pollution should always be treated as an important issue in river system management. On a global scale, acidification is one of the major issues of freshwater pollution. In large regions of Europe and eastern North
America, thousands of lakes, rivers and stream have been damaged through acidification. Acidification of surface waters is due to combination of anthropogenic causes that occur in the catchment themselves and also due to acidifying pollutants that enters into them.
The acidity of water is typically expressed by the pH or proton activity, an intensity factor that reflects the relative balance between H
+
sources and sinks at any given point in time and space. Natural acidification of freshwater ecosytems is a biogeochemical process caused by dissolution of carbonic acid, by fixation of cations (e.g., NH
4
+
, Ca
2+
, Mg
2+
, K
+
) in plants, dissociation of humic acids, oxidation of sulfide minerals, and through other chemical reactions leading to the production of hydrogen ions (H
+
) (Paces.,1994).

7
2.1
Water catchment of Sg. Bekok
As experienced at Sg. Bekok, Batu Pahat in recent years, intensive agricultural drainage infrastructure has contributed to severe water quality problems in the adjacent stream. The river is flowing down all the way from the upper part of the basin to the lower portion where intensive agricultural area with multiple crops
(vegetables, banana and oil palm) can be found along the flood plain of the riverbank. The area along the riverbanks was generally flat with shallow water table and flood prone in nature. Intensive farming activities are taking place in these areas because of easy and direct access to the water supply. Because of the low-lying areas, open drainage canals were constructed up to field level to avoid crops from flooding. The soil types of these areas are young river alluvial and potentially acidic. Water quality problem is noticed in the middle of year 1990 caused by rapid drainage activities at south of Ngamarto area.
2.2
Theoretical background of acidic water development
2.2.1
Peat soil
2.2.1.1 Characteristics of peat soil
Peat is a biogenic deposit which when saturated consists of about 90-95% water and about 5-10% solid material (Warburton, 2004). The organic content of the solid fraction is very high, often up to 95% and is made up of partly decayed remains of vegetation which has accumulated in waterlogged areas over timescales of 100 -1000 years.

8
Peat is physically and chemically complex with its main components being humic and fulvic acids and cellulose. The high organic content of peat is associated with high dissolved organic carbon concentrations in its pore-water i.e water found in the void spaces between sediment particles. The peat initially repel new water; however, continuous rewetting eventually lead to water penetrating all pore spaces, saturating the peat and flushing out any accumulated colour-producing organic acids.
Peat deposits occur in areas where water logging is common. Coulter (1974) has estimated that there are some two million acres of peat in Malaysia, mainly in western Johore, Perak and Selangor, with smaller parts in eastern Johore, Kelantan and Terengganu. Their development is the results of permanent water logging in basin-shaped depressions. Malaysia peat soil is overall known as extremely acidic.
2.2.2.2 Oxidation of pyrite
Peat soil found at agricultural drainage area at Batu Pahat basically consists of pyrite (FeS
2
) (SAJ Holdings Sdn. Bhd., 2003). The formation of pyrite is due to complex reaction between seawater that contains sulfate, give adverse impact to environment through decomposition and deposition of organic matter by wave action over years. Majority of the area involved with pyrite problem located less than ten meters from mean sea level. Previous investigation indicates that the agricultural drainage of the riparian lowland has initiated pyrite oxidation, primarily during dry periods due to lowering of the ground water level.
The construction of an intensive agricultural open drainage canals in an area that are potentially acidic soil would further expose the pyrite layer to the air, and this will increase the amount of hydrogen ion in the soil layer. Further oxidation of sulfate through various stages of redox reaction in the soil end-up with the formation of a low soil pH in the area. The reaction involved in the breakdown of pyrite in the presence of water and oxygen to yield sulphuric acid are well known (Singer &
Stumm, 1970) :

9
FeS
2
(s) + 7/2 O
2
+ H
2
O o Fe
2+
+ 2SO
4
2-
+ 2H
+
(2.1)
FeS
2
+ 1/2 O
2
+ 2H
+ o Fe
2+
+ H
2
Fe
3+
+ 3H
2
O o Fe(OH)
3
+ 3H
+
(2.3)
FeS
2
(s) + 14Fe
3+
+ 8H
2
O o 15Fe
2+
+ 2SO
4
2-
+ 16H
+
(2.4)
Under the gravity flow drainage, surface water in the drains carrying acidic element will eventually flow into the river system. Soluble ions such as H
+
, Fe
2+ and SO
2-
in the soil profile would be transmitted into surface water through leaching process during subsurface runoff. The accumulation of these soluble toxic ions would eventually make the river water more acidic.
2.2.2.3 Biological Sulfur retention
The acidity of streams is influenced by the amount and form of sulfur deposition from atmosphere and by biogeochemical sulfur cycling in the catchment and within streams. Observations in the southeastern U.S and Europe indicate that oxidation of pyrite contributes only a small fraction of the SO
4
2-
flux and acidity in the upland streams compared to atmospheric deposition (Paces 1985).
Sulfate movement through the catchment is primarily regulated by adsorption-desorption reactions in the soil (Figure 2.1). The main process of soil
SO
4
2-
retention in soil is adsorption, a term used generically to indicate any physicochemical SO
4
2-
retention mechanism, including adsorption to Al and Fe oxide surfaces in the soil and precipitation reactions between SO
4
2-
and Al. A decrease in soil pH caused by anthropogenic processes tends to enhance SO
4
2adsorption by increasing the positive charge of the Al and Fe oxide surfaces through protonation.

10
Figure 2.1
Simplified sulfur cycle in the soil
Biological processes play a limited role in long-term SO
4
2-
retention in watersheds (except in peatlands) because sulfur requirements and annual uptake rates by the vegetation are generally modest compared to atmospheric sulfur inputs, especially in high deposition areas. Some microbial immobilization of exogenous sulfur may occur in the organic-rich upper soil; however, this represents only temporary storage and buffering of acidity because the release of similar amounts of
SO
4
2-
during decomposition of organic matter counteracts alkalinity produced with previous strong anion uptake.
Organic-rich peatlands can serve as an important sink of atmospheric SO
4
2-
, primarily through biological processes. The fraction of the input sulfur retained varies among bogs, with the time of the year, and with the total atmospheric sulfur load. Plant uptake in the surface peat accounts for part of the removal of SO
4
2whereas microbial reduction in the anaerobic peat beneath the water table is thought to be the major mechanism of SO
4
2retention. During this process, S
2-
is formed, which can either volatilize as H
2
S or react with organic matter to form carbonbonded sulfur. The alkalizing effect of this SO
4
2-
removal/reduction on the acidity of the drainage water is counteracted when S is reoxidized and SO
4
2-
is released into

solution. This occurs, for example, with a drop of the water table level due to drought.
11
2.2.2
Organic acids (OA)
The terms natural organic acids, dissolved organic carbon (DOC), and aquatic humic substances differ in their definition but are often interchangeably used. In fresh waters, a large fraction of DOC usually qualifies as humic material and is typically acidic.
Organic acids are important agents of freshwater acidity that must be considered in any assessment of watershed acidification. As little as a few mmol/L of natural dissolved organic acids (OA) can acidify dilute water. Extensive survey during past decade suggest that a significant fraction, perhaps as much as one-third, of acidic waters in temperate zones are acidic because of OA (Hemond,1992).
Natural OA in fresh waters originate from the degradation of biomass in the upland catchments, wetlands, near-stream riparian zones, the water column, and sediments. Although soil pore waters in upper soil horizons often contain very high levels of OA (Cronan, 1990), most of this OA does not reach surface waters. It however, sorbed onto mineral soil horizons and is ultimately biodegraded in situ.
Consequently, OA can contribute to acidic episodes if the water flows through upper organic horizons during rain-induced episodes in peaty catchments.
Although complexity and variability hinder precise measurement and characterization, natural OA have a substantially strong acidic character, produce on the order of 5-10 meq H+ /mg organic carbon, lower the pH of natural waters, and decrease the measured Gran acid-neutralizing capacity (ANC) of water.

12
2.2.3
Agricultural activities
Agricultural base economy is widely developed within Batu Pahat area such as palm oil tree, rubber tree and vegetation. As agricultural activities used fertilizers to enhance plant growth, the fertilizers such as ammonium-containing fertilizers are oxidized by bacteria to form nitrate and hydrogen ion which is known to be sources of acidity. For each NH
4
+
cation oxidized, two H
+
are produced. This can be explained in Eqn. 2.5.
(nitrifying bacteria)
NH
4
+
+ 2 O
2 o NO
3
-
+ H
2
O + 2H
+
(2.5)
While most of the identified agricultural pollutants were from commercial fertilizers and pesticides residues and livestock waste, another factor that many of water authority may tend to overlook is the pollutant from the soluble ions in the soil profile. An agricultural activity is known to contribute to oxidation-forming acid processes hence caused acidic water by leaching of acid in soil profile into water.
Although most acidic soils are develop from acidic parents materials, most soils in agricultural land develop acidity by leaching. The source of H
+
ions, which is the initial source of solution acidity can be in various sources as such carbon dioxide from humus decomposition and root respiration. Carbon dioxide from decomposing organic matters and root respiration dissolves in water to form weak acid as illustrate in Eqn (2.6).
CO
2
+ HOH o H
2
CO
3 o HCO
3
+ H
+
(2.6)
Some hydrogen ions are also released by plant roots as hydrogen ions are exchanged for other nutritive cations. In soils, studies have shown pH values as much as 1.2 pH units lower in soil near roots than in the general mass of soil
(Donahue, 1958).

13
2.3
Metal leaching
Upon modification of the agricultural soil through the construction of the drainage canals, toxic elements in the soil would develop especially in the area of young soil along the riverbank and leach into water. The concentration of trace metal in fresh waters is a result of complex competition between processes of adsorption and/or precipitation, on one hand, and formation of soluble complexes on the other. Effect of pH to the presence of metal in water is reported by Illinios state water survey (2003) as in Table 2.1. The darkness in the table describes the significant presence of metal in water.
Nutrient element
Nitrogen
Sulphur
Iron
Manganese
Table 2.1 Effect of pH on the presence of metal pH
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5 8.0
8.5
2.3.1
Ferum
Iron is present at different concentrations in many water and wastewater.
Under anaerobic conditions, several mg/L iron in the form of Fe
2+
can be present whereas concentrations in aerobic surface waters seldom exceeded 0.3 mg/L. Iron is an undesirable component of drinking water because iron hydroxide can form deposits in pipes or cause problems in usage (eg. metallic taste, stains in textiles after washing).
The solubility of iron and manganese is largely controlled by redox conditions (Eqn. 2.7) and pH value. According to Hem (1964), Eqn. (2.7) generally would expected to go to the left; however, at near-neutral pH, when the activity of

14
Fe
2+
is very low and that of Mn
2+
is relatively high, the reaction will go to the right and some replacement of Fe(OH)
3
by MnO
2
will occur.
2 Fe(OH)
3
(s) + Mn
2+
+ 2H
+ o MnO
2
(s) + 4H
2
O + 2Fe
2+
(2.7)
The presence of more than traces of iron in river waters generally indicates pollution by mine water or by iron-pickling wastes, especially if the pH value is low and the acidity high. These wastes may contain iron in the ferrous and/or ferric state. The presence of sulfuric acid tends to stabilize the ferrous iron and delay oxidation to the ferric state. Waters containing appreciable iron or manganese are not suitable for domestic or industrial purposes unless specially treated.
2.3.2
Manganese
Manganese is known to be mobilized from lacustrine sediments. The concentrations of acid-mobilized Mn increase between pH 6.8 and 4.1. The relationship is more distinct in waters from territories with higher deposition rates of strong acids. A drop in the pH values associated with acidification enhances the relative stability of Mn
2+
ions and, at the same time, suppresses the formation of
Mn
3+
and Mn
4+
(oxy) hydroxides (MnO x
). The formation of MnO x
in an acidified environment is likely to proceed only under special conditions, such as microbial and surface catalysis or a sudden increase in the redox potential in oligotrophic waters. A likely explanation for the apparent reversal in mobility is a substantial decrease in Mn concentrations in the most severely acidified terrains, resulting from long-term exposure to acid deposition that has depleted the available Mn in soils.
Another possibility is a higher abundance of waters that are largely unaffected by contact with mineral soils in the group of the most acidic waters, with a pH of
3.8-4.0.

15
2.3.3
Aluminium
Aluminum compounds are abundant in nature and are often found in water.
The salts of aluminum are used extensively in water treatment for the removal of colour and turbidity. Compared with the aluminum intake from food, intake from water is relatively small (Rump, 1988). Ingested aluminum salts do not appear to exert any deleterious effects on man. The incidence of discoloration in drinkingwater in distribution systems increase if the aluminum level exceeds 0.1 mg/l in the final water. A guideline value of 2 mg/l in drinking-water is therefore recommended based on aesthetic considerations.
Concentrations of acid-mobilized Al (Al t
) increase with decreasing pH, from a pH 6.3, and can exceed 2 mg/l at pH<4.4 in terrains with high deposition of strong acids (Vesely et al .1985). Al t
includes organically bound Al (Al o
), Al present in floating suspended matter (minor in acidic waters), and an ecologically dangerous form dissolved inorganic Al (Al i
).
2.4
Limestone treatment
Limestone has been proven effective in neutralizing acid and removing metals from water and wastewater. In recent years, a variety of passive treatment systems have been developed that do not require continuous chemical inputs and that take advantage of naturally occurring chemical and biological processes to cleanse contaminated fresh waters. The primary passive technologies make use of limestone layer in neutralize acid and removing metals which include Anoxic
Limestone Drain (ALD), Alkalinity Producing Systems (APS), Limestone Pond,
Open Limestone Channel (OPC) and Oxic Limestone Drainage (OLD).

16
2.4.1
Characteristics of limestone
Limestone is usually classified as igneous rocks derived from molten masses or magmas. However, there is also some evidence that the origin of some limestone may be attributed to the occurrence of regional metamorphism or preexisting rocks, rearrangement and recrystallization without liquid or molten stage. The rock will display in much variation in composition, appearance, colour, texture, porosity, and hardness.
Two properties similar in most types of limestones are the degree of hardness and the solubility in acid. The essential constituent of limestone is calcite or calcium carbonate (often referred to as carbonate of lime). Pure limestone may comprise of
98 or 99 % of calcite along with other substances.
The colour varies according to composition. Pure limestones are nearly white or cream coloured. Much carbonaceous matter causes the rock to be grey or even black. The texture, porosity, and toughness of the limestone will depend largely upon the nature of the sediment from the consolidation of which it has been formed.
2.4.2
Mechanism of pH adjustment by limestone
When a limestone is added to acidic water, the acid completely dissociates and hydrogen ions are formed. The limestone in water dissolves to a low degree according to Eqn. (2.8) forming Ca
2+
and carbonate ions, CO
3
2-
. The carbonate ions further react with the hydrogen ions forming HCO
3
-
, CO
2
(aq) and CO
2
(g) given in
Eqn. (2.9) to (2.11).
CaCO
3 l Ca
2+
+ CO
3
2-
(2.8)
CO
3
2-
+ H
+ l HCO
3
-
(2.9)
HCO
3
-
+ H+ l CO
2
(aq) + H
2
O

17
CO
2
(aq) l CO
2
(g)
When carbonate ions are consumed by reaction in equation (2.9), more limestone dissolves. According to Shih et al. 2000, reaction in equation (2.8) is very fast, and the rate depends on the property of limestone. Reaction (2.9) is instantaneous; its equilibrium constant is very large, 2.27 x 10
10
m
3
/kg mol at 298 K, thus almost all the carbonate ions are converted by these reactions in acidic solution
(Shih et al . 2000).
As those pair of reactions in Eqn.(2.12) and (2.13) below suggests, limestone reacts with acids (hydrogen ions) to form bicarbonate, and the bicarbonate neutralizes even more hydrogen ions as it converts eventually to carbon dioxide.
Those reactions show how limestone is such as effective buffer to acidification.
H
+
+ CaCO
3 l Ca
2+
+ HCO
3
-
(2.12)
(Limestone) (Bicarbonate)
HCO
3
-
+ H
+ o H
2
CO
3 o Ca
2+
+ HCO
3
-
(2.13)
(Bicarbonate) (Carbonic acid)
Dissolution of calcite (CaCO
3
), which is the principal component of limestone, can neutralize acidity and increase pH in water by the following reactions or some combination thereof:
CaCO
3
(s) + 2H
+ l Ca
2+
+ H
2
CO
3
CaCO
3
(s) + H
2
CO
3 l Ca
2+
+ 2H
2
CO
3
-
(2.15)
CaCO
3
(s) + H
2
O l Ca
2+
+ H
2
CO
3
-
+ OH
-
(2.16)
Where [H
2
CO
3
*] = [CO
2
(aq)] + [H
2
CO
3
] (Plummer et al .,1979; Stumm and morgan, 1996). Hence, the stoichiometric dissolution of 1 mol CaCO
3
will produce
1 mol Ca
2+
and up to 2 mol alkalinity as HCO
3
-
. On the basis of Eqn.(2.15), an alkalinity concentration of 122 mg/l HCO
3
-
equals to 100 mg/l as CaCO
3
, and Ca
2+ concentration of 40 mg/l equals to 100 mg/l as CaCO
3
.

18
The overall rate of calcite dissolution depends on the pH, the partial pressure of CO
2
(Pco
2
), and the activities of H
2
O, Ca
2+
, and HCO
3
-
near the calcite surface
(Plummer et al . 1979; Morse,1983; Arakaki and Mucci, 1995). Generally, the overall rate of calcite dissolution will decrease as the pH and activities of Ca
2+
and
HCO
3
-
increase and the Pco
2
decreases.
2.4.3
Previous studies on limestone treatment
Several investigators have studied the effectiveness of limestone in treating various types of waters and wastewaters. These include treatment of acidic mine drainage (AMD), removal of heavy metal and neutralization of river and lake waters.
Use of limestone in treating waters is rather common these days especially by AMD treatment. It is considered as the least expensive material available for acid neutralization in AMD. Acidic mine drainage is a major source of water contamination in coal and metal-mining districts worldwide. It is one of the largest environmental problems facing the mining industry. Acid mine drainage originates from active and abandoned mine land (AML) when pyrite (FeS
2
) or other metal sulfides associated with mineral deposits are subjected to oxidizing conditions.
Upon exposure to oxygen and water, the sulfide minerals progress through a combination of oxidation and microbial catalyzing reactions to produce large amounts of dissolved metals, sulfate, and acidity (Ziemkiewicz, 1997). The resulting AMD is generally characterized by low pH (<3.5), high acidity (>500mg/L as CaCO
3
) and high concentrations of total dissolved metals (>50mg/L). This acid also dissolves other minerals, releasing cations such as iron (Fe), manganese (Mn) and aluminum (Al). Upon reaching a stream, AMD alters the stream’s chemical balance by consuming alkalinity and introducing metals ions, resulting in a degradation of biological productivity.
Limestone is also capable in removing heavy metal such as Cu, Zn, Cd, Pb,
Ni, Cr, Fe and Mn by batch process or filtration technique. Aziz et al . (2000) has

reported the limestone ability in removing heavy metal in landfill leachate. The removal capability has been reported of up to 90%. Limestone normally remove heavy metal through precipitation resulted from calcite reaction with such ferum, aluminum, zinc and etc.
19
Treatment of surface water from reservoirs for the removal of manganese and particles as well as the adjustment of pH to reach calcium carbonate equilibrium has also been reported by Lipp.
et al . (2000). Prior to limestone filtration, CO
2
was dosed into the reservoir water. The main task of the limestone filtration step is the removal of manganese and the adjustment of pH in order to meet the standard for drinking water requirement.
Contrary to heterotrophic denitrification, autotrophic denitrification consumes alkalinity and, in addition, generates high concentrations of sulfate. In an inadequate buffer system, the pH will decrease during autotrophic denitrification.
Use of limestone as sources of alkalinity control the pH in autotrophic denitrification has been documented by author Koening et al.
(2002).
Lab-scale study for limestone treatment has been done in various types of reactors. It basically depends on the main objectives of the study. Reactor such as
OLD and ALD has been very popular in AMD treatment lab test. Other reactors for limestone treatment include pulsed limestone bed treatment system, novel closedbed limestone reactor, limestone filtration and ultra filtration combined system, limestone fluidized bed treatment and limestone-filled tank.
While limestone is the most cost effective neutralization material available, there is a risk on the tendency for an impermeable metal-hydroxide coating, termed armoring, to form on grain surfaces especially for AMD. Armoring slows the reaction and prevents the limestone from generating any additional alkalinity in the system. Once armored, limestone is assumed to cease dissolution and acid neutralization. Hence, limestone is not recommended for sites with acidity level greater than 50 mg/L as CaCO
3
or Fe concentrations above 5 mg/l.

20
Reactor such as OLD and ALD is designed to avoid armoring and particularly effective for generation of alkalinity. Anoxic limestone drain is commonly used to retard oxidation of Fe (II) to Fe (III), which hydrolyzes and precipitate at a pH of about 3.5. Anoxic limestone drain is a buried, limestone-filled trench that intercepts acidic water before it is exposure to atmospheric O
2
. Retaining
CO
2
within an enclosed ALD can enhance calcite dissolution and alkalinity production. By this mechanism, a greater quantity of alkalinity can be generated in
ALD, which is minimize gas flux, compared to systems such as limestone channels or diversion wells that open to the atmosphere.
Oxic Limestone Drainage is the variation of ALD design for treatment of oxic or highly mineralized water which commonly occurs in mined area. Pulsed flow limestone bed process is another reactor design method to suppressed armor formation. This involves addition of CO
2
into pulsed limestone bed to minimize armor formation and enhances limestone reaction, causing particle-particle abrasion, thus scouring the limestone surface and abrading any coating that form.
Contact time (t
R
) within the treatment is determined by several methods as reported by Charles et al . (1999). Basically the computation of contact time is referring to Darcy’s equation. Usually, data of porosity and flow rate are used to compute the contact time for the water at each point sampled and over the range of flow rates evaluated. The total contact time in the OLD ranged from 1.0 to 3.1 hr has been reported used by Charles et al . (1999).
Table 2.2 illustrated the summary of previous study on water/wastewater treatment using limestone by researcher including various types of water sample.

21
Table 2.2: Previous study on water/wastewater treatment using limestone
Types of water
/wastewater
Surface water from reservoir
Drainage water from coal-ash
Mine water
Initial pH/conc.
Acidity (g/m
3
CaCO
3
Fe (mg/l) = 167
Al (mg/l) = 56
Mn (mg/l) = 9.8
SO
4
(mg/l) = 2200
Acidity (g/m
3
CaCO
3
) = 63
Alkalinity (g/m
3
CaCO
3
) = 0
Fe (mg/l) = 1.8
Al (mg/l) = 0.93
Mn (mg/l) = 3.0 pH = 6.45
Alkalinity (g/m
3
CaCO
3
) =
6.5 pH = 6.43
Mn = 3.15mg/l
Fe = 0.02mg/l
) = 974
Alkalinity (g/m
3
CaCO
3
) = 0
Alkalinity (g/m
3
CaCO
3
)
=74.48
Hardness (g/m
3
CaCO
3
) =
76.82
No3-N (g/m 3 CaCO
3
) = 62.72
Zn = 7.33 mg/l
Period of treatment
(contact time)
3months
(t
R
= 1 to
3.1hr)
1 years
(t
R
= 48hr)
Result pH = 6.5
Acidity (g/m
3
CaCO
3
)= 14
Alkalinity (g/m
3
CaCO
3
) = 64
Fe (mg/l) = 42
Al (mg/l) = 1.0
Mn (mg/l) = 9.6
SO
4
(mg/l) = 2000 pH = 6.6
Acidity (g/m
3
CaCO
3
) = 0
Alkalinity (g/m
3
CaCO
3
)= 108
Fe (mg/l) = 0.003
Al (mg/l) = 0.04
Mn (mg/l) = 2.7
6 weeks pH = 9.35
Alkalinity (g/m
3
CaCO
3
) = 15 g/m 3
495 days pH = 7.55
Mn = 0.49 mg/l
Fe = 0.08 mg/l
HRT
=5.47h
pH = 6.7
Alkalinity (g/m
3
CaCO
3
)
= 207.25
Hardness (g/m
3
CaCO
3
)
= 380.76
NO
3
-N (g/m 3 CaCO
3
) = 6.15
3 months Zn = 5.76 mg/l
References
Charles et al .
1999
Hammarstrom et al . 2003
Lipp et al .
1993
Thornton et al .
1995
Koening et al .
2002
Nuttall et al .
1999

CHAPTER III
METHODOLOGY
This chapter will discuss the method applied for the experimental work including materials used, equipment involved, analysis and experimental procedure.
3.1
Materials and equipments
Actual raw water from three different water samples was used for the experimental work. The samples were taken from three different locations i.e; tributary of Parit Ngamarto, Bekok Intake and Semberong Lagoon. Table 3.1 provides some information of the sampling site. A volume of 30 liters of water sample was collected at each site. Water samples were split into sub samples and stored in sample-rinsed polyethylene container 25L and stored in cold room for preservation purpose.

23
Location
Parit Ngamarto’s tributary
Bekok Intake
Semberong Lagoon
Table 3.1 Characteristic of water sampling location
Characteristics x Reported to be the main sources of acidic water of
Sg. Bekok (SAJ Holdings Sdn. Bhd., 2003) x An artificial constructed drainage x Active agricultural activities is practiced along the drainage (e.g palm oil, banana, vegetables) x Use Sg. Bekok as raw water sources x The point where water is pumped from Sg. Bekok and transmitted to the Semberong Lagoon through pipe line x The point where raw water from Sg Bekok is stored before the water is pumped to the treatment plant i.e Sri Gading and Parit Raja x Act as a reservoir and also for water quality stabilization
The limestone was obtained from Syarikat Air Johor (SAJ). Two limestone sizes i.e 10 – 12 mm and 30 mm of 500 g each, were used for batch-test while 30 mm sizes of 80 kg limestone were used for continuous flow test. Limestone size of
30 mm of 500 g was used for aeration test.
For analytical purpose, chemical reagent used include HACH spectrophotometer reagents for iron and manganese analysis. Table 3.2 shows the list of reagent used for the metal analysis. Preparation of 0.1N NaOH solution for acidity test involved 4 g of NaOH to be dissolved in 1L of distilled water.

24
Table 3.2
Reagents used in metal analysis
Parameter Reagent
Ferum Ferro zinc iron Reagent solution Pillow
Manganese Alkaline Cyanide reagent
Ascorbic acid powder pillows
PAN Indicator solution 0.1 %
Water, deionized
The equipments used in the study include pH meter (WTW pH340 model), magnetic stirrer (Fisher Flexa-mix model), stopped watch (Casio model) and aerator.
3.2
Water quality analysis
Laboratory analysis involved the test on pH, acidity, iron and manganese.
The raw water was analyzed for pH, acidity at pH 4.5 and 8.3, iron and manganese while the treated water was analyzed for pH, iron and manganese. Acidity was measured according to Standard Method (APHA, 1990) while iron and manganese were measured using HACH DR/4000 spectrophotometer which is based on the
Standard Method.
3.2.1
Acidity measurement
In order to measure acidity level at pH 4.5 and 8.3, 0.1 N of NaOH was prepared by dissolving 4 g of NaOH into 1L of distilled water. Water Sample of 100 ml to be analyzed was placed in 200 ml beaker. Initial pH of the water sample was measured and recorded with a calibrated pH meter. By using 50 ml burette, NaOH titrant was titrated by 0.2 - 0.5ml increment into the water sample until the final pH reached 9.

Acidity is expressed in terms of mg/L as CaCO
3
. It is calculated by using formula below:
25
Acidity {
( mL NaOH titrant ) u ( normality NaOH ) u 50000 mL water sample
(3.1)
3.2.2
Iron and Manganese
Iron and manganese were analyzed using HACH DR/4000 spectrophotometer
(Figure 3.1). The method used was adapted from the Standard Method (1990).
Analysis of Iron was carried out using Method 8008 (Ferro Ver Method). The estimated detection value for the method ranges from 0.008 to 3 mg/l Fe.
Manganese was analyzed using Method 8149 (PAN Method). The estimated detection value for the method ranges from 0.005 to 0.7 mg/l Mn.
Figure 3.1
HACH DR/4000 Spectrophotometer

26
3.3
Experimental procedure
The experiment was conducted in 2 modes of test which are batch mode test and continuous flow test. This is followed by an aeration test conducted in batchmode.
3.3.1
Batch-mode study
The batch mode study was conducted to investigate the viability of limestone to treat the acidic raw water. It was carried-out to obtain some insight on the required contact time needed for the pH of the raw water to be raised up to pH 5.5-7 as required by the Malaysia National Water Quality Standard. The results would then be compared to the previous work conducted using synthetic water (Muslim,
2006). Two limestone sample sizes i.e. 10 -12.5 mm and 30 mm of 500 g were used in the study. Each sample of limestone was prepared to treat water sample of Sg.
Sedi, a tributary of Sg. Bekok.
BEAKER 2000ml
LIMESTONE SPECIMEN
RAW WATER pH METER
MAGNETIC STIRRER STOPPED-WATCH
Figure 3.2
The set-up of batch mode study

27
As shown in Figure 3.2, limestone was submerged in the water by hanging it in nylon net. The mixing of the water was achieved by a magnetic stirrer. The experiment started with the full submergence of limestone in the water. The pH reading was taken at specific interval up to 1 hour using pH meter. The interval was set to every 1minute for the first 5 minutes, every 5 minutes for the next 15 minutes and every 10 minutes for the next 20 minutes. The test was however stopped if the pH reached 7 at any recorded time
3.3.2
Continuous-flow study
The experiments were conducted using a reactor systems consist of four limestone drain as shown in Figure 3.3 & 3.4. The system was of plug-flow type and the water was let flowing by gravity force. Each limestone drain was 20 cm in diameter with length and depths of 0.67 m and 14 cm, respectively. The drain was constructed using PVC pipe that was split lengthwise to form semicircular trough.
After lining the trough with PVC paste, a total of 20 kg, 3 mm limestone size was placed in each drain. At the end of each reactor drain, a pipe was connected to allow water to pass through to the next reactor drain.
As shown in Figures 3.4, the 30 liters of water sample was put in the storage tank prior to each experimental run. The volumetric flow rate was set by recording the time for the first effluent to exit the last reactor. This also represent the contact time of the water with the limestone. Three contact times were used for each water sample i.e. 30 min (88 mL/min), 60 min (42 mL/min) and 120 min (21 mL/min).
The pH of the water was monitored at the inlet and outlet of each reactor drain. The water sampled at the exit of the fourth reactor was used for Fe and Mn analysis.

STORAGE
TANK
LIMESTONE-DRAIN
28
Figure 3.3
The set-up of limestone-drain reactor outflow
Figure 3.4
Continuous flow-mode test

29
According to Darcy’s equation (Freeze and Cherry 1979), the velocity of flow through a porous medium is given as v = Q / (A . n) (3.2) where Q is the volumetric flow rate, A is the cross-sectional are perpendicular to flow, and n is the porosity.
Volumetric flow rate in this experimental work was estimated using another form of Darcy’s equation (Hedin and Watzlaf, 1994):
Q = ( Ms . n / U b
) / t
R
(3.3) where M s
is mass of limestone and U b
is bulk density of the limestone. The numerator of Eqn. (3.3) also indicates the void volume. The porosity, n of the limestone was estimated to be 0.5 ( = 500 ml / 1000 ml = V v
/ V
T
) while the bulk density, U b of limestone was determined to be 15100 kg/m
3
.
3.3.3
Aeration test
The aeration test was conducted to determine the effect of aeration on limestone treatment. The test was conducted in the same manner as in the batchmode test as shown in Figure 3.5. Two tests were conducted i.e. one with aeration while the other without aeration (as control). A limestone size of 30 mm at 500 g of weight was used in the study to treat raw water sample of Semberong lagoon.

Figure 3.5
Batch-mode treatment test conducted under aeration.
30

CHAPTER IV
RESULTS AND ANALYSIS
This chapter discusses the results obtain from the experimental work. The results were analyzed to gain understanding on the limestone behavior as neutralizing agent. Factors such as acidity, flow rate and contact time were considered as the variable that affect the neutralizing process.
Figure 4.1 shows the pH profile of raw water treated with limestone. One of the beakers contained 10 – 20 mm diameter limestone while the other contained 30 mm diameter (both weight 500 g) namely, W4S4-R and W4S5-R. The initial pH of the water was 4.7. As can be observed, the pH with smaller diameter of limestone rise at a faster rate as compared to the other. The former reached pH 7 within 3 minutes while the latter within 10 minutes.

32
7.50
6.50
5.50
4.50
3.50
2.50
W4S4
W4S3
W4S2
W4S1
W4S4-R
W4S5-R
Masa (h:mm:ss)
Figure 4.1
Effect of limestone size on neutralizing acidic raw water
This finding agrees with those of Muslim (2006). While this study used actual raw river water as compared to Muslim (2006) who used synthetic water, the results indicate the significance of limestone size in altering the pH of the acidic water. The results also show the viability of limestone as insitu treatment in treating the acidic water.
4.2 Continuous flow study
As already being mentioned, three water samples collected from Parit
Ngamarto’s tributary, Bekok Intake and Semberong Lagoon were used in the experimental work. Table 4.1 shows the characteristics of each of the water sample.
The water from the tributary of Parit Ngamarto was the most acidic one with acidity more than 7 times higher than the other two.

Table 4.1 Characteristic of the water sample.
Initial pH
Acidity (mg/l as CaCO
3
)
Fe (mg/l)
Mn (mg/l) tributary
2.5
530
0.39
0.53
2.9
75
0.40
0.09
Semberong lagoon
3.1
51
0.30
0.06
33
The iron and manganese content in all the water samples were considered low as it fulfill the required standard of Malaysia National Water Quality Standard
(Revised December 2004).
4.2.1
pH
The pH readings were monitored at the inflow, outflow and three intermediate points within the limestone reactor drain. As the water passed through the drains it contacted more limestone and this is expressed in term of kg of limestone in the following discussion.
4.2.1.1 Parit Ngamarto’s tributary
The results of the limestone treatment on Parit Ngamarto’s tributary water sample are given in Table 4.2. Figure 4.2 illustrates the profile of pH of the water as it passed through the drains. The pH of the water rise as the water flow through the limestone drain indicating the effect of the limestone amount on the pH treatment.
As expected, the water which has the longest contact time with the limestone produce highest pH level at a faster rate. At 30 min, 60 min and 10 min contact

times, the final pH after contacted with 80 kg of limestone was 4.1, 4.7 and 5.2 respectively.
34
Table 4.2
pH reading for Parit Ngamarto tributary at every sampling point
Contact time,min
30 min
60 min
120 min
0
2.5
2.5
2.5
* As the water flow through the reactor drains
Limestone weight, kg
20
2.8
3.2
3.4
40
3.0
3.8
4.0
60
3.9
4.1
4.2
80
4.1
4.7
5.2
5.5
5
4.5
4
3.5
3
2.5
2
0
88 mL/min
42 mL/min
21 mL/min
20 40 60
Limestone weight,kg
80 10 0
Figure 4.2
Profile of pH increase for different contact time of Parit Ngamarto’s tributary water sample

35
4.2.1.2 Bekok Intake
As mentioned earlier, Bekok Intake is the point where raw water from Sg.
Bekok is pumped into pipeline to be transmitted to Semberong lagoon. Initial pH at the point during sampling has been recorded around 2.9 with acidity of 75 mg/L as
CaCO
3
. The results of the limestone treatment are shown in Table 4.3. Figure 4.3 illustrates the profile of pH of the water as it passed through the drains. The final pHs were 5.9, 6.0 and 6.3 after flowing through 80 kg of limestone at 30, 60 and 120 mins contact time, respectively.
Table 4.3
pH reading for Bekok Intake at every sampling point
Contact time,min
30 min
60 min
120 min
0
2.9
2.9
2.9
20
3.7
3.6
4.5
Limestone weight, kg
* As the water flow through the reactor drains
40
4.3
4.3
5.6
60
5.1
5.4
5.9
80
5.9
6.0
6.3
7
6.5
6
5.5
5
4.5
4
3.5
3
2.5
2
0
88 mL/min
42 mL/min
21 mL/min
20 40 60
Limestone weight,kg
80 100
Figure 4.3
Profile of pH increase for different contact time of Bekok Intake water sample

36
4.2.1.3 Semberong Lagoon
Initial pH at the lagoon was recorded around 3.1 with acidity of 51 mg/L as
CaCO
3
. With higher pH and lower acidity among other water samples, the pH of the water was observed to increase faster than other samples. The results were shown in
Table 4.4 while Figure 4.4 depicted the ability of limestone treatment in raising the pH of the water as it flow through the drains. At different contact time, the final pH achieved were 6.5, 6.9 and 7.1 at contact time of 30, 60 and 120 mins respectively.
Table 4.4 pH reading for Semberong Lagoon at every sampling point
Contact time,min
30 min
60 min
120 min
0
3.1
3.1
3.1
20
3.6
3.8
4.2
Limestone weight, kg
40
4.2
5.0
5.2
60
5.3
5.7
6.2
80
6.5
6.9
7.1
5
4.5
4
3.5
3
2.5
2
7.5
7
6.5
6
5.5
0
88 mL/min
42 mL/min
21 mL/min
20 40 60
Limestone weight,kg
80 100
Figure 4.4
Profile of pH increase for different contact time of Semberong lagoon water sample

37
4.2.2
Comparative analysis
Based on the results obtained from the experimental work, it can be observed that the amount of limestones, level of raw water acidity and contact time between the limestone and the raw water seems to have a significant effect on the performance of the limestone treatment. This agrees with the findings of Muslim
(2006). The longer the water is exposed to the limestone, the greater the extent of the pH rise. Similar pattern is observed with the amount of limestone used.
Figure 4.5 illustrates the effect of initial pH and acidity to the final pH of the water after in-contact with 80 kg of limestone. Eventhough the three water samples taken have different initial pH but they are not significantly differ as the pH ranged between pH 2.5 and 3.1. However the acidity of the waters ranged from 520 to 51 mg/l as CaCO
3.
It is thus suspected that the different value of the acidity of the samples that significantly affect the rate of the pH and the extent rise.
Water with low pH and high acidity level is known to be strongly acidic.
With respect to this, tributary of Parit Ngamarto’s raw water can be categorized as strongly acidic among the samples. This is anticipated due to the soil condition of
Parit Ngamarto areas which comprised of peaty land, pyrite layer in addition to the contribution from agricultural as discussed in Section 2.2.2.2. Due to this, the treatment could not even reach minimum pH standard for raw water as required in
Malaysia National Water Quality Standard i.e. pH5.5 after two hours of contact with the limestone.
For the other two water samples i.e; Bekok Intake and Semberong Lagoon, with acidity under 100 mg/l as CaCO
3,
the pH rise was much faster with the limestone treatment and was able to achieve the required pH standard after 30 min of contact time with limestone. Eventhough Sg Bekok receive water discharge from
Parit Ngamarto , the acidity of the water was found to reduce very much at the time the water reach the Bekok Intake. Dilution factor could have assisted in reducing the acidity of the water.

38
8
7
6
5
4
3
2
1
0
Min pH Standard
520 72
Acidity, mg/L as CaCO3
51
Figure 4.5
Effect of acidity on pH adjustment.
As mentioned earlier, the water flowed by gravity passing through four stages of limestone-drain with each drain filled with 20 kg of limestone. As it passed through the limestone, the pH of the water increased. This was due to the dissolution of limestones which produce alkalinity (HCO
3
-
) and thus increase the pH. The dissolution rate is enhanced mainly by the chemical reaction of H
+
with OH
-
within liquid film that surrounds the limestone particle. In general, the pH value increases as the dissolution rate increase. The generation of alkalinity has been discussed by
Shih et al . (2000) as shown in Eqn. (2.12).
H
+
+ CaCO
3 l Ca
2+
+ HCO
3
-
(2.12)
(Limestone) (Bicarbonate)
4.2.3
Statistical Analysis
Statistical analysis was conducted to quantitatively determine the significance of limestone amount, contact time (flow rate) and acidity in affecting the efficiency of the limestone treatment. Analysis of variance (ANOVA) was conducted on the

39 results of the study. The analysis was carried out using Microsoft Excel. The results of the analysis are shown in Tables 4.5 to 4.8.
Table 4.5 ANOVA for sample of Parit Ngamarto tributary
Source of
Variation
Contact time
SS df MS
0.932
2.000
0.466
F
7.684
0.014
4.459
Limestone weight 8.253
4.000
2.063
Error 0.485
8.000
0.061
34.005
0.000
3.838
Total 9.671
14.000
Table 4.6 ANOVA for sample of Bekok Intake
Source of
Variation SS df MS
Contact time 1.554
2.000
0.777
Limestone weight 19.180
4.000
4.795
Error 0.757
8.000
0.095
F
8.204
50.644
0.012
0.000
4.459
3.838
Total 21.491
14.000
Table 4.7 ANOVA for sample of Semberong Lagoon
Source of
Variation SS df MS F
Contact time 0.909
2.000
0.455
9.762
0.007
Limestone weight 26.242
4.000
6.561
140.916 0.000
Error 0.372
8.000
0.047
4.459
3.838
Total 27.524
14.000

Table 4.8 ANOVA for acidity
Source of
Variation SS df
Acidity 7.480
2.000
Contact time 0.815
2.000
Error 0.159
4.000
MS
3.740
0.408
0.040
F
94.292
10.276
P-value F crit
0.000
0.027
6.944
6.944
Total 8.454
8.000
40
The significance of the parameter was based on the p-value. A p-value lower than 0.1 indicate the significant of the parameter at 90% confidence level while a p-value of lower than 0.05 indicate the significant of the parameter at 95% confidence level. As shown in Table 4.6 to 4.9, the p-value of contact time, limestone and acidity were lower than 0.05. This indicates that the variables are significantly affecting the pH of the water sample at 95% confidence level.
For Table 4.5 to 4.7, the analysis of variance of the three water samples shows similar trends where p-value of the amount of limestone was lesser than pvalue of contact time. This indicates the significance of limestone amount as compared to contact time in affecting the pH rise. For Table 4.8, analysis of the whole samples has show the significance of acidity as compared to contact time in affecting the pH rise.
4.2.4
Iron (Fe)
As can be seen in Table 4.9, initial Fe concentration for the three samples were almost similar where Parit Ngamarto tributary and Bekok Intake recorded values around 0.4 mg/l while lagoon recorded a concentration of 0.304 mg/l.
Despite the Fe concentration being lower the recommended Standard, experiments were still conducted to determine the effect of limestone treatment on the iron

content of the water. The effect of limestone treatment on the Fe concentration is shown in the Table 4.9 and Figure 4.6.
41
Table 4.9 Fe removal at different contact time
Sample
Pt Ngamarto’s tributary
Bekok Intake
Lagoon
Initial
(mg/L)
0.39
30 min
Effluent
(mg/L)
0.02
% removal
95
0.40
0.30
0.03
0.15
94
50
Contact time
60 min
Effluent
(mg/L)
0.01
% removal
97
120 min
Effluent
(mg/L)
0.03
% removal
93
0.03
0.12
94
62
0.02
0.16
95
47
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Standard of Fe initial
30 min
60 min
120 min
Pt Ngamarto Intake
Contact time,min
Lagoon
Figure 4.6
Removal of iron in the water samples at different contact time
From Table 4.9, Fe was found removed effectively up to 90% for the sample of Parit Ngamarto’s tributary and Bekok Intake. As active armoring due to high acidity occurred within limestone treatment, Fe has seen removed efficiently in the two water samples. The initial Fe concentration of both samples were recorded

42 around 0.4 mg/L. At any contact time, the final concentration was recorded ranged between 0.03 to 0.02 mg/L. For lagoon sample, the percentage of Fe removal was ranged between 47 to 62% with initial concentration of 0.3 mg/L and final concentration at any contact time recorded around 0.12 to 0.16 mg/L.
Figure 4.7
Armoring occur at the last limestone drain
The reduction of Fe concentration seems to be due to the armoring of the Fe to the limestone as can be observed by the orange-yellow coatings on limestone located near the outflow of the drain (Figure 4.7). Armoring is the term used for an impermeable metal-hydroxide coating that forms grain surfaces on limestone.
The discussion on armoring has been given in section 2.4.3. Although armoring is the indication of metal removal, it actually slows the neutralizing reaction as it prevents the limestone from generating any additional alkalinity in the system. Due to this circumstance, the ability of limestone to further increase the pH in water would be disrupted. This can be seen through result of pH adjustment in
Figure 4.6. Once armored, limestone is assumed to cease dissolution and acid neutralization. Thus, while Fe was removed effectively by the process, in long term, it will possibly slow down the neutralization process. Hammarstom et al . (2003) has reported that limestone is not recommended for sites with acidity level greater than

43
50mg/L as CaCO
3
or Fe concentrations above 5mg/L due to the tendency of armoring. Parit Ngamarto tributary had record acidity of 530 mg/L as CaCO
3
while acidity of Bekok Intake was 72mg/L as CaCO
3
which both indicates value that greater than 50 mg/L.
4.2.5
Manganese
Table 4.10 shows the Mn removal by limestone treatment at different contact times. As shown in Figure 4.7, the tributary of Parit Ngamarto’s water sample has much higher initial Mn concentration than the other samples. The water contains
0.53 mg/l of Mn as compared to less than 0.1 mg/l (0.09mg/l and 0.062mg/l respectively) for Bekok Intake and lagoon is lower the required standard. Despite the Mn concentration in Bekok Intake and lagoon water sample’s being lower the recommended Standard, experiments were still conducted to determine the effect of limestone treatment on the Mn content of the water.
The initial concentration of Parit Ngamarto’s tributary was exceeded the raw water standard limit of 0.2 mg/L. The treatment required 2 hours to reduce the Mn.
Removal of Mn was found effective with the longer contact time. As can be seen from Table 4.10, the percentage of Mn removal was recorded increased from 9% to
69% (Parit Ngamarto’s tributary), 38 to 49% (Bekok Intake) and 2 to 23% (lagoon) with the increased of contact time. The removal efficiency also has seen influence by the acidity of the water samples. With acidity of 520 mg/L as CaCO
3
, Parit
Ngamarto’s tributary has recorded final percentage of Mn removal up to 69% at 2 hours contact time, followed by Bekok Intake (49%) and lagoon (23%).

44
Sample
Pt Ngamarto’s tributary
Bekok Intake
Lagoon
Table 4.10 Mn removal at different contact time
Initial
(mg/L)
0.53
30min
Effluent
(mg/L)
0.48
% removal
9
Contact time
60min
Effluent
(mg/L)
0.27
% removal
49
120min
Effluent
(mg/L)
0.16
% removal
69
0.09
0.06
0.06
0.06
38
2
0.05
0.05
44
19
0.07
0.05
49
23
0.6
0.5
0.4
0.3
1
0.9
0.8
0.7
0.2
0.1
0
Initial
30 min
60 min
120 min
Pt Ngamarto Intake contact time,min
Lagoon
Figure 4.7 Removal of Mn in the water samples at different contact time
Removal of metal concentration i.e. Mn and Fe is influence by sorption and coprecipitation mechanism. The autocatalytic sorption and coprecepitation reaction which was proposed by Hem (1964) explain the removal of Mn
2+
and dissolve trace metal within limestone reactor as:
2 Fe(OH)
3
(s) + Mn
2+
+ 2H
+ o MnO
2
(s) + 4H
2
O + 2Fe
2+
(2.7)
As has been explained in section 2.3.1, Eqn (42.7) is generally expected to go to left; however, at near-neutral pH, when the activity of Fe
2+
is very low and that of

Mn
2+
is relatively high, the reaction will go to the right and some replacement of
Fe(OH)
3
by MnO
2
will occur. Thus, Mn
2+
precipitation will be active as water is near-neutral pH.
45
The overall process indicated by the equation has generally explained the result illustrated in Figure 4.8. As final pH of Parit Ngamarto’s tributary water approached neutral at two hours contact time with limestone concentration of Mn was observed to reduce with 69% of removal.
4.3
Aeration study
In an attempt to enhance the rate of CaCO
3
dissolution, aeration study was conducted as a cheaper alternative. It is hypothesized that by aerating the water, the
CO
2
produced CaCO
3
from dissolution will be removed and thus increase the dissolution rate as relate to Eqn (2.9), (2.10) and (2.11):
CO
3
2-
+ H
+ l HCO
3
-
(2.9)
HCO
3
-
+ H+ l CO
2
(aq) + H
2
CO
2
(aq) l CO
2
With one run as a control, Figure 4.10 shows the effect of aeration to the limestone treatment on the pH of the water sample. The pH of both samples was observed to increase together in the early phase of treatment. After pH reached 5.0, sample with aeration was found to rise faster than the sample without aeration. The final pH of both samples after 1 hour contact time was 7.1 and 6.6, respectively.
Although the different was not quite significant as expected, it actually took 40 minutes for the aerated sample to reach the pH achieved by non-aerated. While this results showed some positive indication on the role played by the aeration, further studied are needed to confirm and understand the phenomenon.

6
5
4
8
7
3
2
1
0
0 with aeration without aeration
10 20 30 40 contact time,min
50
Figure 4.9 Effect of aeration to pH
60 70
46

CHAPTER V
5.1
Conclusions conclusions could be made. This is as listed below: i) ii) iii) iv) neutralizing reagen t of acidic raw water of Sg. Bekok.
The results also demonstrates the capability of limestone in removing metal
(i.e. Fe and Mn) from actual raw water.
The effectiveness of limestone treatment is affected by several factors which include the acidity of the raw water, the amount of limestone used and the contact time (or flow rate) between the limestone and the water.
Minimum contact time for the pH to rise to accepted value (5.5) range from 30 min to more than hours.
5.2
Recommendations
E search in order to reduce the contact time of the limestone treatment. Some recommendations for further studies are suggested as listed below:

i) ii)
To study the effect of aeration on the limestone treatment process. process.
iii) To enhance the surface area of the limestone.
48

49
REFERENCES
Anderson, D.O. (2005). Labile aluminium chem istry downstream treated lake and an ffects of warm winters and ex Science of the
Total Environment .
APHA (2002).
Standard Method for Examination of Water and Wastewater.
21 st
Asia Water & E Kerja-kerja Pemulihan Sistem Saliran
Kg.Ngamarto dalam Kawasan Tadahan Sg Bekok:Conceptual Integrated River
Basin Management Plan . Johor: Syarikat Air Johor Sdn Bhd.
chemical removal of iron from semi-aerobic landfill leachate by limestone filter.
Water Management. 24:353-358.
Biswas, A. K Water resources: environment planning, management and development . McGraw-Hill.
Charlotte, A.N. and Paul, L.Y
inc removal from hard, circum-neutral mine waters using a novel closed-bed limestone reactor. Water Resources . 34(4):
1262-1268.
Chereminisinoff, P. N. (1993). Water management & supply: water and wastewater treatment guidebooks . E

50 neutralize acidic mine drainage. Journal of Environmental Quality 32(4):
12771289.
Cravotta III, C. A. and Trahan, M.K
1999). Limestone drain to increase pH and remove dissolved metals from acidic mine drainage, Applied Geochemistry .
14:581-606.
Donahue, R. L. (1958).
Soils, an introduction to soils and plant growth . Prentice-
Hall,Inc.
Chemical dynamics in freshwater ecosystems . Lewis Publisher.
limestone reacted with acid-mine drainage in a pulsed limestone bed treatment system at the Friendship Hill Historical Site, Pennsylvania,USA . Applied
Geochemistry . 18:1705-1721.
Henrikson, L. and Brodin, Y Liming of acidified surface water: A
Swedish synthesis . Swedish: Springer.
Restoring acid waters: lochFleet 1984-
1990 . London and New Y l sevier Applied Science
(2001). Impact of agricultural drainage on stream water q , Jurnal
Teknologi, 31(F): 67-77.
K Design practices for covered drains in an agricultural land drainage system, a worldwide survey . India: International commission on irrigation and drainage India.

51
K Mining and the freshwater environment :
K River pollution; chemical analysis . London Butterworths.
K limestone for pH control in autotrophic
Journal of Biotechnology . 99:161-171.
Lipp, P. Schmitt, A. and Baldauf, G. (1997). Treatment of soft reservoir water by limestone filtration in combination with ultrafiltration .
Desalination.
113:285-292
Norotny, V. and Chesters, G. (1981).
Handbook of nonpoint pollution sources & management . Van Nostrand Reinhold company.
North, F..J.(1930) Limestones: The origins, distribution, and uses. Guildford: The
Woodbridge Press, Ltd.
Malaysia Water Industry Guide (2004) , Malaysia National Water Quality Standards
(Revised December 2004) , International Water Association.
Muslim, R. (2006). Pelarasan pH air mentah dengan menggunakan batu kapur.
Skudai, Johor:.Univers iti Teknologi Malaysia.
Rump, H.H. and K ist, H. (1988).
Laboratory Manual for the Examination of water,
Wastewater and soil.
German: Federal Republic of Germany.
Shih, S.M. Lin, J.P. and Shiau, G.Y
. Dissolution rates of limestones of different sources.
Journal of Hazardous Material . B79:159-171.
Steinberg, C.E
Acidification of freshwater ecosystems implications for future . LOndon :Wiley Publisher.

52
Thibodeaux inetics of peat soil dissolved organic carbon release to surface water. Part 2: A chemodynamic process model.
Chemosphere.
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Thornton, F. C. (1995). Manganese removal from water using limestone-filled tanks ,
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W.vanLoon,G. and Duffy, S.J. (2005). Environmental chemistry a global perspective.
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Warburton, J. Joseph, H. and Andrew, J.
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Acid mine drainage treatment with armoured limestone in open limestone channels.
Journal of Environmental Quality . 26(4): 1017-1024.

APPENDIX A
Table A1: Data for Batch-mode test
Date
Time
Experiment
13.06.2006
2.26 PM
W4S4-R
28 ºC Temperature
Size
Initial pH
10-12.5mm
4.71
Volume of water 1000ml
Weight 100g t(h:mm:ss) pH
0:00:00 4.71
0:01:00
0:02:00
0:03:00
5.8
6.68
7.1
0:04:00 7.27
Date
Time
Experiment
Temperature
Size
Initial pH
Volume of water
Weight
13.06.2006
3.00 PM
W4S5-R
28 ºC
30mm
4.68
1000ml
100g t(h:mm:ss) pH
0:00:00 4.68
0:01:00
0:02:00
5.21
5.63
0:03:00
0:04:00
5.88
6.1
0:05:00
0:10:00
6.33
7.01
53

Table B1: Data for aeration test
Date
Time
29.08.2006
11PM
Experiment Without aeration
Temperature 28 ºC
Size 30mm
Initial pH
Volume
Weight
3.12
1000ml
500g t(h:mm:ss) pH
0:00:00 3.12
0:01:00 3.72
0:02:00
0:03:00
0:04:00
0:05:00
4.02
4.19
4.4
4.49
0:10:00
0:15:00
0:30:00
0:40:00
0:50:00
1:00:00
4.7
4.98
5.8
6.1
6.34
6.59
APPENDIX B
Date
Time
29.08.2006
11PM
Experiment With aeration
Temperature 28 ºC
Size 30mm
Initial pH
Volume
Weight
3.12
1000ml
500g t(h:mm:ss) pH
0:00:00 3.12
0:01:00 3.68
0:02:00
0:03:00
0:04:00
0:05:00
0:10:00
3.95
4.16
4.39
4.49
4.75
0:15:00
0:30:00
0:40:00
0:50:00
1:00:00
4.89
6.19
6.61
6.95
7.14
54

APPENDIX C
Table C1: Data of acidity titration
(a) Parit Ngamarto (b) Bekok Intake
5.08
5.6
5.76
6.11
6.44
6.69
7.07
7.82
8.46
4.24
4.29
4.34
4.49
4.53
4.55
4.62
4.76
4.85
3.14
3.2
3.48
3.75
3.94
4.06
4.12
4.15
4.2
pH
2.48
2.51
2.57
2.63
2.65
2.74
2.87
3.01
NaOH
0
0.2
0.4
0.6
1
1.3
1.6
1.8
8.5
8.7
9
9.3
9.5
9.7
10
10.2
10.5
7.5
7.7
8
8.2
5
5.5
6
7
7.2
3.5
3.7
4
4.5
2
2.3
2.7
3
3.2
pH
2.89
2.91
2.92
3.52
4.1
5.17
9.1
NaOH
0
0.2
0.5
0.7
1
1.2
1.5
(c) Semberong lagoon pH
3.12
3.71
4.05
4.34
8.08
9.24
NaOH
0
0.2
0.5
0.7
1
1.2
55

5
4
3
2
1
0
0
9
8
7
6
2 4 6
NaOH
8 10
Figure C1(a) Acidity titration for Parit Ngamarto
12
10
9
8
7
6
5
4
3
2
1
0
0 0.2
0.4
0.6
0.8
NaOH
1 1.2
Figure C1(b) Acidity titration for Bekok Intake
1.4
1.6
56

10
9
8
7
6
5
4
3
2
1
0
0 0.2
0.4
0.6
NaOH
0.8
1
Figure C1(c) Acidity titration for Semberong Lagoon
1.2
1.4
57

APPENDIX D
Malaysia National Water Quality Standards (Revised December 2004)
Table 4D Recommended Raw water Quality Criteria
Parameters Column I Column II
Acceptable Value mg/l
(unless otherwise stated)
Source of Reference
Total Coliform
Turbidity pH
Iron(as Fe)
Manganese
5000 cfu/100ml
1000NTU
5.5 – 9.0
1.0
150
WHO1
WHO2
WHO1
MAL
WHO1
MAL
WHO1
WHO2
MAL
Refer to WHO International Standard for Drinking Water 1963
Refer to WHO Guideline for Drinking Water Quality Volume 1&2 1984
Refer to values adapted for Malaysia conditio
58