LEAD AND CADMIUM REMOVAL IN SYNTHETIC WASTEWATER...

LEAD AND CADMIUM REMOVAL IN SYNTHETIC WASTEWATER USING

CONSTRUCTED WETLAND

MOHD SHAHREL B BAHARUDIN

A thesis submitted in fulfilment

of the requirements for the award of the degree of

Bachelor of Chemical Engineering

(Biotechnology)

Faculty of Chemical & Natural Resources Engineering

Universiti Malaysia Pahang

MAY, 2008

ii

DECLARATION

I declare that this thesis entitled “LEAD AND CADMIUM REMOVAL IN

SYNTHETIC WASTEWATER USING CONSTRUCTED WETLAND” is the

result of my own research except as cited in references. The thesis has not been

accepted for any degree and is not concurrently submitted in candidature of any other

degree.

Signature :……………………………………….

Name of Candidate : Mohd Shahrel B Baharudin

Date : 16th

May 2008

iii

DEDICATION

Special Dedication to my beloved mother (Norhan) and father (Baharudin), for their

love and encouragement.

And,

Special Thanks to my friends, my fellow course mates and all faculty members.

For all your care, support and best wishes.

Sincerely,

Mohd Shahrel B Baharudin

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ACKNOWLEDGEMENT

First and foremost, I would like to express my sincere appreciation to my

supervisor, Pn. Noor Ida Amalina bt. Ahamad Nordin, for constantly guiding and

encouraging me throughout this study. Thanks a lot for giving me a professional

training, advice and suggestion to bring this project to its final form.

I am very thankful to the staff of Chemical & Natural Resources Engineering

Faculty, Universiti Malaysia Pahang for their cheerfulness and professionalism in

handling their work. In preparing this project, I was in contact with many people,

researchers, academicians and practitioners. They have contributed towards my

understanding and thoughts.

In particular, my sincere thankful is also extends to all my colleagues and

others 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.

And last, but not least a special thanks to my parents and other family members for

their continuous support while completing this project.

v

ABSTRACT

Heavy or toxic metals are harmful to humans and other organism even in

small quantities. This research focused on the removal efficiency of the heavy

metals (lead and cadmium) using constructed wetland system. Constructed wetlands

are the low cost engineered systems that have been designed and constructed to

utilize the natural processes involving wetland vegetation, soils, and the associated

microbial assemblages to assist in treating wastewaters. In addition, constructed

wetland treatment had demonstrated the good capacity in treating the wide range of

wastewaters including the hazardous industrial waste. In this research, the free water

surface constructed wetland was conducted in the batch mode system and loaded

with Pistia stratiotes (water lettuce) in order to study the removal efficiency of

cadmium and lead elements. From the study, it was found that the Pistia stratiotes is

an aquatic plant that growing rapidly and also a high biomass crop with an extensive

root system that can enhance the heavy metals removal. There were two parameters

studied in this research which were varying in number of plant, and varying pH

conditions. The removal of lead and cadmium in the constructed wetland were

increased when the numbers of plant increased. The constructed wetland containing

15-plants recorded the highest removal with 99.28% for lead removal and 65.89%

for cadmium removal. For the pH condition experiment, the neutral condition (pH =

7) showed the better removal compared to the base and acidic conditions. As a

conclusion, constructed wetland system with wetland plant (Pistia stratiotes) showed

good removal efficiency for lead and cadmium from the industrial wastewater.

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ABSTRAK

Logam berat atau logam toksik adalah sangat berbahaya kepada manusia dan

organisma lain walaupun di dalam kuantiti yang kecil. Kajian yang dilakukan ini

telah memfokus terhadap kecekapan penyingkiran logam berat (plumbum dan

kadmium) dengan menggunakan tanah bencah buatan. Tanah bencah buatan

merupakan sistem berkos rendah yang telah diubahsuai dimana ianya direka dan

dibina untuk menjalankan proses semulajadi yang melibatkan tumbuh-tumbuhan

tanah bencah, tanah, serta himpunan mikrob tanah bencah itu sendiri bagi membantu

dalam rawatan sisa cecair. Tambahan pula, rawatan ini telah menunjukkan hasil

yang baik di dalam merawat pelbagai jenis sisa cecair termasuklah sisa industri yang

sangat berbahaya. Di dalam kajian ini, kaedah rawatan tanah bencah jenis

permukaan air bebas telah dijalankan dalam keadaan sistem berkelompok serta akan

ditumbuhkan dengan Pistia stratiotes (kiambang) bagi mengkaji kecekapan

penyingkiran elemen kadmium serta plumbum. Kajian sebelum ini menunjukan

bahawa Pistia stratiotes merupakan tumbuhan yang tumbuh dengan pantas serta

merupakan tumbuhan berjisim biologi tinggi yang mempunyai sistem akar

bersambungan bagi menggalakan proses menyingkiran logam berat. Parameter yang

telah dikaji di dalam kajian ini adalah perbezaan dari segi jumlah tumbuhan, serta

perbezaan pH. Tanah bencah buatan yang mempunyai 15 pokok telah mencatatkan

penyingkiran yang paling tinggi iaitu 99.82% untuk penyingkiran plumbum

manakala 65.89% untuk kadmium. Bagi eksperimen pelbagai pH pula, tanah bencah

buatan pada pH neutral (pH = 7) menunjukkan peyingkiran logam yang baik

berbanding dengan kondisi berasid dan beralkali. Kesimpulannya, sistem rawatan

tanah bencah dengan menggunakan tumbuhan tanah bencah tertentu seperti (Pistia

stratiotes) menunjukan kecekapan penyingkiran yang baik terhadap elemen

plumbum dan kadmium daripada sisa cecair industri.

vii

TABLE OF CONTENTS

CHAPTER

TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xiii

LIST OF APPENDICES

xv

1 INTRODUCTION 1

1.1 Background of Study 1

1.2 Objective 2

1.3 Scope of Study 2

1.4 Problem Statement

3

2 LITERATURE REVIEW 5

2.1 Wetland 5

2.2 Natural Wetland 6

2.3 Constructed Wetland 6

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2.3.1 Types of Constructed Wetlands 8

2.3.2 Free Water Surface Wetland 8

2.3.3 Subsurface Flow Wetland 9

2.4 Wetland Plants 10

2.4.1 Water-lettuce (Pistia stratiotes) 11

2.5 Heavy Metals 12

2.5.1 Heavy Metal in Industrial Waste 13

2.6 Heavy Metal Treatment Mechanism by

Wetland Plant

14

2.6.1 Phytoextraction 14

2.6.2 Hyperaccumulation 14

2.6.3 Rhizofiltration 15

2.6.4 Phytostabilation 15

2.7 Metal Analysis 15

2.7.1 Flame Atomic Absorbance

Spectroscopy

16

2.7.2 Atomic Absorption Apparatus

16

3 METHODOLOGY 19

3.1 Design of Constructed Wetland 20

3.2 Wetland Plants Collection 22

3.3 Designing the Artificial Wastewater 22

3.4 Experiments 22

3.4.1 Varying Number of Plant

Experiment

22

3.4.2 Varying pH Condition Experiment 23

3.5 Water Sampling and Analysis

23

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4 RESULTS AND DISCUSSIONS 24

4.1 7 Days of Treatment (Using 15 Plants)

Observation

24

4.2 Varying Number of Plant Experiment 26

4.3 Varying pH Condition Experiment

28

5 CONCLUSIONS AND RECOMMENDATIONS 30

5.1 Conclusions 30

5.2 Recommendations

31

REFERENCES 32

APPENDIX 35

x

LIST OF TABLES

TABLE NO.

TITLE PAGE

2.1 Examples of applications and efficiency of

wetlands for quality improvement of water

7

2.2 Physical description of water lettuce

12

2.3 Some flame used in absorption spectroscopy

17

xi

LIST OF FIGURES

FIGURE NO.

TITLE PAGE

2.1 (a) Free water surface wetland with free floating

plant, (b) Free water surface wetland with

emergent macrophytes

8

2.2 (a) Constructed wetland with horizontal sub-

surface flow, (b) Constructed wetland with

vertical sub-surface flow

9

2.3 Division of constructed wetland plants

10

2.4 Water-lettuce

11

2.5 Flame atomic absorbance spectrometer

18

3.1 The framework of study

20

3.2 Constructed wetland design for the experiment

21

4.1 The concentration of lead remaining in the

wastewater after 7 days of treatment for

Treatment Using Wetland and No Treatment.

25

4.2 The concentration of cadmium remaining in the

wastewater after 7 days of treatment for

Treatment Using Wetland and No Treatment.

26

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4.3 Percentage of Lead removal from the wastewater

after 7 days of treatment for blank, 5-Plants, 10-

Plants and 15-Plants.

27

4.4 Percentage of Cadmium removal from the

wastewater after 7 days of treatment for blank, 5-

Plants, 10-Plants and 15-Plants.

28


after 7 days of treatment for blank, pH-5, pH-7,

and pH-9

29


after 7 days of treatment for blank, pH-5, pH-7,

and pH-9

29

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LIST OF SYMBOLS

(C2H5)4Pb - Tetraethyllead

µM - Micromolar

AA - Atomic absorption

Al - Aluminum

As - Arsenic

Ba - Barium

BOD5 - Biochemical oxygen demand

Cd - Cadmium

Cd(NO3)2 - Cadmium nitrate

Co - Cobalt

COD - Chemical oxygen demand

Cu - Copper

CWs - Constructed wetlands

Fe - Ferum

FWS - Free water surface

HCl - Hydrochloric acid

HNO3 - Nitric acid

L - Liters

mM - Milimolar

Mn - Manganese

NaOH - Sodium hydroxide

Ni - Nickel

Pb - Lead

Pb(NO3)2 - Lead nitrate

PbO·PbSO4 - Monobasic lead sulfate

PbS - Lead sulfide

PbSO4 - Lead sulfate

xiv

Se - Selenium

SF - Surface flow

Sr - Strontium

TKN - Total Kjeldahl nitrogen

V - Vanadium

Zn - Zinc

xv

LIST OF APPENDICES

APPENDIX

TITLE PAGE

A.1 Table for the cadmium blank data in term

of concentration remaining.

35

A.2 Table for the cadmium blank data in term

of percentage removal.

35

A.3 Table for the lead blank data in term of

concentration remaining.

36

A.4 Table for the lead blank data in term of

percentage removal.

36

A.5 Table of the varying number of plants

experiments for cadmium element (in term

of concentration remaining).

36



of percentage removal).

37


experiments for lead element (in term of

concentration remaining).

37

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percentage removal).

38

A.9 Table of the varying pH condition


of concentration remaining).

38



of percentage removal).

39



concentration remaining).

39



percentage removal).

40

B.1 Apparatus for sampling (micropipette and

sample bottles).

41

B.2 Atomic Absorption Spectrometer (AAS)

41

B.3 Lead (II) Nitrate and Cadmium Nitrate

Tetrahydrate (chemical used to make the

synthetic waste)

42

B.4 Series of standard solution (for Lead and

Cadmium analysis)

42

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C.1 Plant condition after day 1 of no. of plant

experiment (a) 5 plants, (b) 10 plants, (c)

15 plants.

43

C.2 Plant condition after day 15 of no. of plant

experiment (a) 5 plants, (b) 10 plants, (c)

15 plants.

43

C.3 Plant condition after day 1 of varying pH

experiment (a) pH-5, (b) pH-7, (c) pH-9.

44

C.4 Plant condition after day 15 of varying pH

experiment (a) pH-5, (b) pH-7, (c) pH-9.

44

CHAPTER 1

INTRODUCTION

1.1 Background of Study

Constructed wetlands are engineered systems that have been designed and

constructed to utilize the natural processes involving wetland vegetation, soils, and

their associated microbial assemblages to assist in treating wastewater (Vymazal,

2007). In the simple phrase, constructed wetlands can be defined as “man-made”,

“engineered” or “artificial” wetlands. Despite treating the wastewater, constructed

wetland also can be an attractive natural landscape where wildlife builds habitat and

for human visit.

Much interest has been focused on constructed wetlands for removing toxic

metals from wastewater in recent years (Raskin and Ensley, 2000). There are four

aspects on how the heavy metals are accumulated by plants in constructed wetland

systems, which are; bioaccumulation, phytoextraction, phtostabilation and

rhizofiltration.

Constructed wetlands are being considered as a sustainable, low-investment

and low maintenance cost technology that can complement or replace conventional

water treatment (Tack et al., 2007). Nowadays, many industrial investors are

looking to fix the constructed wetland systems into their wastewater management

system. They noticed that the constructed wetland can minimize the energy

consumption and operational cost.

2

Recent studies show that constructed wetlands can treat the wide range of

wastewaters including the hazardous industrial waste. The industrial wastewater

usually contains a certain amount of heavy metals like lead and cadmium. These

heavy metals are the hazardous pollutants to human and animals even in the small

portion of them. Cadmium is discharged to the environment by the metal plating and

battery industries. While, the higher lead concentration can be find in the petroleum

refinery and steelwork industrial effluent.

The selection of appropriate wetland plant species in constructed wetland is

important in making the constructed wetland functioned effectively in heavy metals

removal. Plant species have the variety of capacity in removing and accumulating

heavy metals (Zayed et al., 1998). Therefore, some plant uptakes on heavy metals

were varied based on their species. Water-lettuce (Pistia stratiotes) is an aquatic

plant that growing rapidly and also a high biomass crop with an extensive root

system that able enhance the heavy metals removal.

1.2 Objective

The objective of this study is to investigate the removal efficiency of the

heavy metals (lead and cadmium) using constructed wetland system.

1.3 Scope of Study

The study was focused on the effect of constructed wetland in treating

industrial wastewater. In this experiment, the constructed wetland was designed with

the same plant species, which is water lettuce (Pistia stratiotes) species. This

experiment also focused on the lead and cadmium removal from industrial

wastewater using constructed wetland. The treatment was conducted for 7 days. The

scopes for this study were:

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1. To construct the wetland with water lettuce (Pistia stratiotes) plant species.

2. To focus on the treatment of lead and cadmium containing wastewater.

3. To study the removal efficiency of lead and cadmium when:

a. The numbers of plants are increased.

b. The pH is varies.

The experiment was carried out at the Faculty of Chemical Engineering and

Natural Resources Laboratory, Universiti Malaysia Pahang.

1.4 Problem Statement

Toxic heavy metals in air, soil, and water are global problems that are a

growing rapidly in the development area. Industrial wastes that contain heavy metals

cause an unreasonable risk to human health and safety, property, and the

environment.

The exposure of heavy metals can cause disorder to the human body system.

Furthermore, this type of waste has the potential to contribute in mortality and

increase the serious irreversible illness. Acute lead poisoning in humans causes

severe failure in the kidneys, reproductive system, liver, brain and nervous system.

Cadmium exposure is also harmful to human as it causes high blood pressure, kidney

damage and cancer.

The technology for treatment and disposal of the industrial wastes must be

efficient in order to overcome this problem. Constructed wetland is an economic

treatment system that has received much attention recently. In this system, wetland

plants play an important role in heavy metals removal. Therefore, appropriate

selection of wetland plant species in constructed wetland can exploit the removal

potential of heavy metals by wetland plants (Liu et al., 2007).

4

The approach in managing a constructed wetland is constantly the vital issue

that consecutively makes this system functioned efficiently in removing the heavy

metals. Thus, the well managed constructed wetland through the proper treatment

makes this system as an alternative method in treating industrial wastewater.

CHAPTER 2

LITERATURE REVIEW

2.1 Wetland

Wetland are areas where water covers the ground surface or is present at the

ground surface for varying periods of time during the year. The prolonged presence

of water creates conditions that favor the growth of specially adapted plants

(hydrophytes) and promote the development of characteristic wetland (hydric) soils.

Although wetlands are often wet, a wetland might not be wet year-round. In fact,

some of the most important wetlands are only seasonally wet. Wetland occur at the

interface between land and water and are transition zones where the flow of water,

the cycling of nutrients, and the energy of the sun meet to produce a unique

ecosystem. The wetland ecosystem is characterized by unique hydrology, soils, and

vegetation that make these areas as the important features of a watershed. Wetlands

are among the most productive ecosystem in the world, comparable to rain forests

and coral reefs, as well as they perform a variety of ecological functions. The

combination of shallow water, high levels of nutrients, along with primary

productivity is ideal for the development of organisms that form the base of food

web and feed many species of fish, amphibians, shellfish, and insects. Wetlands are

points of ground-water recharge, absorb water, take up airborne pollutants, ease

floodwater, control erosion, cycle minerals (nitrogen), produce organic matter

through carbon fixation, and provide feeding refuge and reproductive habitats for a

wide variety of fish and wildlife (Chin, 2006).

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2.2 Natural Wetland

Natural wetlands can be broadly classified as either coastal wetlands or inland

wetlands, where coastal wetlands are influenced by alternate floods and ebbs of tides

while inland wetlands are nontidal. Coastal wetlands may be further categorized as

either marine or estuarine wetlands (Chang, 2002), depending on whether they are

adjacent to an open ocean or adjacent to an estuary. In contrast to coastal wetlands,

inland wetlands are most common on floodplains along rivers and streams (riverine

wetlands), in isolated depressions surrounded by dry land (palustrine wetlands),

along littoral zones of lakes and ponds (lacustrine wetlands), and in other low-lying

areas where the ground water intercepts the soil surface of where precipitation

sufficiently saturates the soil. Riverine and lacustrine wetlands are sometimes

collectively referred to as riparian wetlands. Wetlands are typically classified as

marshes, swamps, bogs, or fens (Chin, 2006).

2.3 Constructed Wetland

Constructed wetlands (CWs) are engineered systems that have been designed

and constructed to utilize the natural processes involving wetland vegetation, soils,

and the associated microbial assemblages to assist in treating wastewaters. They are

designed to take advantage of the same processes that occur in natural wetlands, but

possesses within a more controlled environment. CWs for wastewater treatment may

be classified according to the life form of the dominating macrophyte into systems

with free-floating, rooted emergent and submerged macrophytes (Brix and Schierup,

1989).

Constructed wetlands have traditionally been used for the treatment of

domestic along with municipal sewage from both separate and combined sewerage.

However, since the late 1980s CWs have been used for many other types of

wastewater, including agricultural wastewaters, mine drainage, food processing

wastewaters, heavy industry wastewaters, landfill leachate and runoff waters

efficiently. For more examples, refer to Table 2.1. Since that, constructed wetlands

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are being considered as a sustainable, low-investment and low maintenance cost

technology that can complement or replace conventional water treatment (Tack et al.,

2007).

Table 2.1 : Examples of applications and efficiency of wetlands for quality

improvement of water (Otte and Jacob, 2006)

Type of pollutant Efficiency (% removal)

Macronutrients

Ammonium-N 16-67

Nitrate/Nitrite 40

Total Kjeldahl nitrogen (TKN) 49-81

Organic nitrogen 82

Soluble Reactive Phosphate (SRP) 56

Total-P (TP) 44-68

Metals and Metalloids

Al 81-97

As 65

Ba 70-95

Cd 58-71

Co 39-98

Cu 49-65

Fe 91-97

Mn 91-99

Ni 22-67

Se 69

Sr 24-51

Zn 52-95

V 100

Organic compounds, including

explosives

63-100

Coliform bacteria 26-98

Eggs of human parasites 94-100

COD 81

BOD5 72-89

Suspended solids 43-94

LEAD AND CADMIUM REMOVAL IN SYNTHETIC WASTEWATER...

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