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NATIONAL UNIVERSITY OF RWANDA
Zinc and Chromium removal mechanisms from
industrial
wastewater by water hyacinth, Eichhornia
crassipes (Mart.) Solms-Laubach
John GAKWAVU RUGIGANA
MSc. Thesis in WREM November 2007
National University of Rwanda
Faculty of Applied Sciences
Department of Civil Engineering
In collaboration with
Zinc and Chromium removal mechanisms from
industrial
wastewater by Water hyacinth, Eichhornia
crassipes (Mart.)
Solms-Laubach
Master of Science Thesis
in
WATER RESOURCES AND ENVIRONMENTAL
MANAGEMENT
(W.R.E.M)
by
John R. GAKWAVU
Supervisors
Mr. B. C.
SEKOMO (PhD Research Fellow/ UNESCO-IHE)
I. NHAPI, PhD.
(UNESCO-IHE & National University of Rwanda)
A Thesis submitted in partial fulfilment of requirements of
the Master of Science degree in Water
Resources and Environmental Management
(WREM) at the National University of Rwanda
NUR, November 2007
Statement of originality
I declare that this research report is my own work;
unaided work. It is being submitted for the degree of Master of Science in the
National University of Rwanda. It has not been submitted before for any degree
of examination in any other University.
Gakwavu Rugigana John
Date: November 10th, 2007
Signature:
When wastewaters are not well purified they can seriously
damage surface and
ground water. They can also endanger human and animal
health.
The findings, interpretations and conclusions expressed in
this study do neither necessarily reflect the views of the National University
of Rwanda, Faculty of Applied Sciences nor of the individual members of the MSc
committee, nor of their respective employers.
Table of Contents
Statement of originality iii
Table of Contents v
List of tables viii
List of figures ix
List of symbols and abbreviations x
Dedication xi
Acknowledgements xii
Abstract xiii
1 INTRODUCTION 1
1.1 Background 1
1.2 Problem description 2
1.3 Objectives 3
1.4 Research questions 3
1.5 Hypotheses 4
1.6 Scope of the research 4
1.7 Report outline 4
2 LITERATURE REVIEW 5
2.1 Overview on use of macrophytes in metal removal 5
2.2 Water hyacinth (Eichhornia crassipens (Mart.) Solms. 6
2.2.1 Systematic position 7
2.2.2 Ecological factors 8
2.2.3 Potentials and constraints in using of water hyacinth 8
2.3 Heavy metals 9
2.4 Wastewater 11
2.5 Foliar absorption 12
2.6 Translocation of metals within plants 12
2.7 Uptake 13
Zinc and chromium removal mechanisms from industrial
wastewater by water hyacinth (Eichhornia crassipes) (Mart.)
Solms-
Laubach
3 MATERIALS AND METHODS 15
3.1 Water Hyacinth sampling site description 15
3.2 Methods 16
3.2.1 Description 16
3.2.2 Synthetic wastewater solution preparation 16
3.2.3 Experimental Procedures 16
3.3 Sample Analyses 19
3.3.1 Relative Growth 19
3.3.2 Bioconcentration Factor 19
3.3.3 Metals Accumulation 20
4 RESULTS AND DISCUSSIONS 22
4.1 Variations on plant relative growth 22
4.1.1 Relative growth of water hyacinth plants 22
4.1.2 Discussions on relative growth of water hyacinths 23
4.1.3. Correlation between final fresh weight and relative growth
23
4.2 pH effects and metal concentrations remained in controls
(blanks) 24
4.2.1 pH effects in blank samples 24
4.2.2 Zinc concentrations remaining in blank samples 24
4.2.3 Chromium concentrations remained in blank samples 25
4.2.4 Discussions of pH effects on metal concentrations in blank
samples 26
4.3 pH variations and Zn(II) and Cr(VI) concentrations in water
samples with water
hyacinths 26
4.3.1 Variations of pH on metal removal by the plants 26
4.3.2 Zinc concentrations remaining in water samples after 4
weeks of
experiment. 28
4.3.3 Chromium conc. remaining in water after 4 weeks of
experiment 29
4.3.4 Discussions on pH variations and metal removal by the
plants 29
4.4 Bioconcentration Factor (BCF) for zinc and chromium 30
4.4.1 Bioconcentration Factor for zinc 30
4.4.2 Bioconcentration Factor for chromium 30
Zinc and chromium removal mechanisms from industrial
wastewater by water hyacinth (Eichhornia crassipes) (Mart.)
Solms-
Laubach
4.4.3 Discussions on bioconcentration factor 31
4.5 Bioaccumulation 32
4.5.1 Adsorption of Zinc by water hyacinth plants 32
4.5.2 Total adsorption of zinc 33
4.5.3 Adsorption of chromium by water hyacinth plants 34
4.5.4 Discussions on adsorption mechanism 35
4.6 Uptake mechanism 35
4.6 1 Uptake mechanism for zinc 35
4.6.2 Uptake mechanism for chromium 36
4.6.3 Discussions on uptake mechanism 36
4.7 Translocation Ability (TA) 37
4.7.1 Variation of translocation ability for zinc 37
4.7.2. Variation of translocation ability for chromium 39
4.7.3 Discussions on translocation ability 41
5. CONCLUSIONS AND RECOMMENDATIONS 42
5.1 Conclusions 42
5.2 Recommendations 43
References 44
Appendices 50
Zinc and chromium removal mechanisms from industrial
wastewater by water hyacinth (Eichhornia crassipes) (Mart.)
Solms-
Laubach
List of tables
Table 2.1: Maximum growth response of water hyacinth exposed to
Cd and Zn 12
Table 2.2: Chromium uptake by water hyacinths during a period of
17 days from Keith
et al., 2006 13
Table 2.3: copper uptake by water hyacinth
during a period of 17 days.from Keith et
al., 2006 14
Table 2.4: Arsenic uptake by water hyacinth
during a period of 17 days from Keith et
al., 2006 14
Table 4.1: variations on bioconcentration factor of zinc 31
Table 4.2: variations on bioconcentration factor of chromium
31
Table 4.3: Variability in zinc uptake compared to initial
concentration & exposure time.
37
Table 4.4: variability in uptake of chromium 37
Table 4.5: Translocation ability of chromium by the plant 40
Table 4.6: variations in translocation ability of zinc 41
List of figures
Figure 2.1: Common aquatic plants (source: Aquatics, 2005) 6
Figure 2.2: Morphology of water hyacinth plant (source: Aquatics,
2005) 8
Figure 3.1: Topographic map showing the location
of Nyabugogo swamp and its
influents 15
Figure 3.2: Plan view of experimental set up.
18
Figure 3.3: steps in lab experiment. 18
Figure 4.1: Relative growth of water hyacinth plants vs exposure
time for different Zn
and Cr concentrations 23
Figure 4.2: Correlation between Relative Growth of plants and
Final Fresh Weight 24
Figure 4.3: variations of pH in blank samples 24
Figure 4.4: Zinc conc. remaining in blank water samples over time
25
Figure 4.5: Chromium conc. remaining in blank water samples over
time 26
Figure 4.6: pH variations in plant water samples over time 27
Figure 4.7: Zinc conc. remaining in water samples with water
hyacinth plants over time
28
Figure 4.8: Chromium conc. remaining in water samples with water
hyacinth plants 29
Figure 4.9: Bioconcentration factor of Zinc 30
Figure 4.10: Bioconcentration factor of Chromium 31
Figure 4.11: Desorption of Zinc after 1 week 33
Figure 4.12: Desorption of Zinc after 2 weeks 33
Figure 4.13: Desorption of Zinc after 4 weeks 33
Figure 4.14: Total desorption of Zinc 34
Figure 4.15: Desorption of Chromium 34
Figure 4.16: Variations of uptake for zinc by the plants 35
Figure 4.17: Uptake of chromium in plant tissues for different
initial concentrations 36
Figure 4.18: Translocation ability for Zinc by water hyacinth
plants 38
Figure 4.19: Translocation ability for 1 week 38
Figure 4.20: Translocation ability for 2 weeks 39
Figure 4.21: Translocation ability for 4 weeks 39
Figure 4.22: Comparison of roots and shoots in translocation
ability 40
Figure 4.23: Correlation of roots vs. shoots 40
List of symbols and abbreviations
AAS: Atomic Absorption Spectrometer
ANOVA: Analysis of variance
APHA: American Public Health Association
AWWA: American Water Works Association
BCF: Bioconcentration factor
BOD5: Biological oxygen demand during 5 days
CGIS: Geographic Information System and Remote Sensing Center.
Cr: Chromium
EDTA-Na2: Ethylen diethyl tetracetate disodium
et al.: Et alii
FFW: Final fresh weight
IFW: Initial fresh weight
ppm: Part per million
RG: Relative growth
SPSS: Statistical Package for the Social Sciences
TA: Translocation ability
US.EPA: United States Environment Protection Agency
WEF: Water Environment Federation
Zn: Zinc
Dedication
To my beloved family.
Acknowledgements
The achievement of this research was possible with the
contribution of several persons with their continued remarks, comments,
encouragement, their financial and moral supports, etc. to whom I would like to
thank you.
First of all, I am very grateful to the Almighty God for his
mercy during my studies and research. I'm also grateful to Rwandan Government
for the financial support to complete this Master's Programme.
In particular, my heartfelt thanks to my supervisor PhD.
candidate SEKOMO BIRAME Christian and my co-supervisor Dr. Innocent Nhapi, for
their acceptance to supervise this research, their particular remarks,
scientific discussions, critical comments, their availability and their
encouragement. My thanks go also to all UNESCO-IHE and NUR staffs who had
direct and indirect contributed to my studies at this juncture. I am also
indebted to the laboratory personnel of National University of Rwanda,
especially Jean Nepomuscene and Dominic of the Department of Chemistry from the
Faculty of Sciences, NUR.
I can not close my acknowledgements without to thank all WREM
colleagues cohort for their individual contribution, their sharing ideas
through certain modules, their scientific discussions during some hard moments,
for their cooperation and team spirit.
Furthermore, I greatly acknowledge my family, for being always
with me in every single steps of this thesis with their encouragement.
To everyone concerned by this research, please found your place
in my grateful thanks.
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