Upload
hoangdung
View
216
Download
0
Embed Size (px)
Citation preview
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
iv
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.
vi
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
viii
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
ix
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
xii
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
4.5 Percentage of Lead removal from the wastewater
after 7 days of treatment for blank, pH-5, pH-7,
and pH-9
29
4.6 Percentage of Lead removal from the wastewater
after 7 days of treatment for blank, pH-5, pH-7,
and pH-9
29
xiii
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
A.6 Table of the varying number of plants
experiments for cadmium element (in term
of percentage removal).
37
A.7 Table of the varying number of plants
experiments for lead element (in term of
concentration remaining).
37
xvi
A.8 Table of the varying number of plants
experiments for lead element (in term of
percentage removal).
38
A.9 Table of the varying pH condition
experiments for cadmium element (in term
of concentration remaining).
38
A.10 Table of the varying pH condition
experiments for cadmium element (in term
of percentage removal).
39
A.11 Table of the varying pH condition
experiments for lead element (in term of
concentration remaining).
39
A.12 Table of the varying pH condition
experiments for lead element (in term of
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
xvii
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:
3
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).
6
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
7
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