ABSTRACT
A natural filtration on sludge drying bed has resulted to a modified equation incorporating the
compressibility coefficient. The equation was derived using the application of a modified
FMTLXLYLZ dimensional analysis technique. The equation was validated using experimental
data from a pilot scale sand drying bed and there was a close agreement between theory and
experiment with a correlation coefficient ranging from 0.94 to 0.98. The experimental slope and
intercept was found to be (1260913.48 s/m6 , 4872.53 s/m3) (5359604.57 s/m6, 844882.56 s/m3),
(112117050.4 s/m6, -2135816.16 s/m3), and (145562880 s/m6, -30497917.03 s/m3) while the
theoretical values of slopes and intercepts are (1257426.75 s/m6, 5270.26 s/m3),( 4579418.42
s/m6, 905658.24 s/m3), (112117075 s/m6, -21358166.74 s/m3),and (206699290.5 s/m6, –
4589555.58 s/m3) respectively.
TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Abstract iv
Acknowledgment v
List of Tables vi
List of figures vii
List of symbols viii
Table of content ix
CHAPTER ONE: INTRODUCTION 1
1.1 Sludge and sand drying bed
1.2 Research Problem 2
1.3 Objective of project 2
1.4 Justification of project 2
1.5 Scope of study 3
CHAPTER TWO: LITERATURE REVIEW
2.1 Sludge treatment process 4
2.1.1 Thickening 4
2.1.2 Stabilization 4
2.1.3 Conditioning 5
2.1.4 Disinfection 6
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2.1.5 Dewatering 7
2.1.5.1 Vacuum filtration 7
2.1.5.2 Centrifuge 7
2.1.5.3 Belt filter press 8
2.1.5.4 Filter Press 8
2.1.5.5 Conventional sand drying bed 8
2.1.5.6 Paved drying bed 9
2.1.5.7 Artificial media drying beds 10
2.1.5.8 Vacuum-assisted drying bed 11
2.2 Drying 11
2.3 Definition of Terms 11
2.31 Specific Resistance 11
2.3.2 Compressibility coefficient 14
2.4 Limitation of Carman’s Equation 16
2.4.1 Variability of (R) during filtration process 17
2.4.2 The problem of variable hydrostatic head 17
2.4.3 Relationship between volume and time. 18
2.4.4 Relationship between volume and area of filtration 18
2.4.5 The concentration Term 18
2.4.6 Relationship between R and P 19
2.4.7 Area of filtration 19
2.5 Apparatus used in filtration experiment 19
2.6 Filtration Theories 21
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2.6.1 Almy and Lewis (1912) 21
2.6.2 Sperry (1916) 21
2.6.3 Baker (1921) 22
2.6.4 Weber and Hershey (1926) 22
2.6.5 Carman (1934, 1938) 22
2.6.6 Ruth (1933, 1935) 23
2.6.7 Tiller (1953) 24
2.6.8 Grace (1953) 24
2.6.9 Rushton et al (1973) 25
2.6.10 Anazodo (1974) 25
2.6.11 Gale and White (1975) 26
2.6.12 Hemant (1981) 26
2.6.13 Ademiluyi jo , Anazodo and Egbuniwe (1982) 27
2.6.14 Ademiluyi (1984) 28
2.6.15 Ademiluyi et al (1982, 1987) 28
2.6.16 Agunwamba et al (1988) 29
2.6.17 Ademiluyi (1991) 30
CHAPTER THREE: RESEARCH METHODOLOGY
3.1 Study Area 31
3.2 Materials and Method 31
3.3 Dimensional analysis 33
3.4 Theory of Experiment 34
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3.5 Method of evaluating filtration parameters 39
3.5.1 Initial solid content 39
3.5.2 The Area of filtration 39
3.5.3 The compressibility coefficient 39
3.5.4 Density of filtrate 39
3.5.5 Dynamic Viscosity 39
3.5.6 Weight of dry solid 40
3.5.7 Specific Resistance of sludge 40
3.5.8 Thickness of Dry sludge 40
3.5.9 Time of Filtration 40
3.5.10 Volume of Filtrate 40
3.5.11 Percentage of solid content expressed in decimal 40
CHAPTER FOUR: RESULTS AND DISCUSSIONS
4.1 Experimental validation of equation 41
4.2 The Effect of chemical conditioning on the specific resistance 44
4.3 Variation of Initial solid content with specific resistance 47
4.4 Variation of Hydrostatic pressure with specific resistance 47
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION 48
REFERENCES 52
APPENDIX I 57
APPENDIX II 58
APPENDIX III 67
APPENDIX IV 74
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CHAPTER ONE
INTRODUCTION
1.1 SLUDGE AND SAND DRYING BED DEWATERING
Domestic wastewater result from the use of water in dwellings of all types and includes
water after use and the various waste materials added: body waste, kitchen waste, household
cleaning agents and laundry soap and detergents. In contrast to the general uniformity of
substances found in domestic waste water, industrial waste water show increasing variation as
the complexity of industrial processes rises. The character of these waste materials is such that
they cause significant degradation of receiving waters and hence results to environmental health
hazard and pollution. One of the steps in the control of pollution is the treatment of waste water
before disposal. In the process of treating waste water, sludge is generated and constitutes the
most challenging problem facing the environmental engineer. This sludge has high water content
and is usually subjected to dewatering to reduce the moisture.
Sludge drying bed is one of the earliest processes used in the dewatering of sludge before
the introduction of mechanical processes. The waste can be dewatered in an open or covered
sand bed which also requires a large amount of land for its operation. Sand drying bed is affected
by such uncontrollable factors as Rainfall, Humidity and Temperature. The process is cost
effective and easy to operate than the mechanical system and usually produces sludge cake of
about 25-40% solid.
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1.2 RESEARCH PROBLEM
The dewatering of sludge using vacuum filtration theory has been adopted in full scale in
the 1920s. Since then, various contributors for example Carman, 1934; Ruth, 1935; Coackley,
1958; Heertjes, 1964; Gale R.S, 1967; Anazodo, 1974; Ademiluyi j o, 1981etc) have been
presenting equations aimed at improving the performance of the vacuum filtration process.
However, their research was limited to experimental work which could not provide an insight
into the interactive nature of sludge filterability since filterability is an interactive property
expressing the relationship between the suspension to be filtered and the filtering medium.
1.3 OBJECTIVE OF PROJECT
The objective of the project is to present sand drying bed equation that will account for
compressibility coefficient through the application of a modified FMTLXLYLZ dimensional
approach.
1.4 JUSTIFICATION OF PROJECT
The general lack of agreement between experiment and theory in sludge filtration under
constant vacuum filtration approach discovered by the body of researchers has led to great
controversies which have resulted to the modifications of filtration equations as is contained in
literature. Therefore, this research opens new direction into the nature of sludge filtration
phenomenon and will enable new research into the natural filtration method which may result to
an end to the present controversies.
1.5 SCOPE OF STUDY
The sludge used for this study is limited to domestic sludge from the University of
Nigeria Nsukka waste treatment site. No chemical analysis of the filtrate and the sludge were
carried out.
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