ABSTRACT
Bioremediation has been proven to be the most effective method of cleaning up oil
contaminated soils through the application of nutrients and microorganism to contaminated
soils. Hence, this research was aimed at investigating the effects of particle sizes on
bioremediation of crude oil polluted sandy soils. Six different soil samples were sieved using
the B.S sieve sizes. The sieve sizes were classified into X and Y such that X is fine to coarse
sand while Y is very fine to coarse sand according to U.S Bureau and PRA (Public Roads
Administration) soil classification system. The soil samples were polluted with escravous
sweet crude oil at a uniform rate of concentration under aerobic condition. Treatment
commenced after four days using nutrients and microorganism. Soil samples were examined
for physiochemical and microbial characteristics for a period of 42days. The parameters
examined were: moisture content, particle size distribution, total hydrocarbon content, soil
pH, available nitrogen, available phosphorus, total heterotrophic bacteria and fungi count.
The analysis of the soil characteristics throughout the remediation period showed that total
heterotrophic bacteria and fungi counts increased in all the soil samples. THBC was highest
in sample G for both fine to coarse sand(X) and very fine to coarse sand (Y ) with values of
250cfux105/g and 298 cfux105/g at least values of Cu and D50 respectively. There was a
decrease in nitrogen, phosphorus, organic carbon content, moisture content, pH and total
hydrocarbon content. The result of the study revealed that, the rate of hydrocarbon loss was
higher in samples with less Cu and D50 values compared to samples of higher values, an
indication that particle size distribution parameters could be one of the factors affecting
bioremediation. The correlation coefficient(r) of THC versus Cu for fine to coarse sand(X) is
0.867 while for very fine to coarse sand is 0.923.
TABLE OF CONTENTS
TITLE PAGE i
CERTIFICATION PAGE ii
DEDICATION iii
ACKNOWLEDGEMENT iv
TABLE OF CONTENTS v
LIST OF TABLES ix
LIST OF FIGURES x
LIST OF ABBREVIATIONS xi
ABSTRACT xiii
CHAPTER ONE
1.0 Introduction 1
1.1 Background of Study 1
1.2 Statement of Problem 3
1.3 Significance of Study 3
1.4 Objective of Study 3
1.5 Scope of Study 4
1.6 Limitation 4
CHAPTER TWO
2.0 Literature Review 5
2.1 Cohessionless Soils 5
2.2 Particle Size Distribution and Index Properties 5
2.2.1 Sand Percentage 5
2.2.2 Soil Colour 6
2.2.3 Soil Texture 6
2.2.4 Soil Aggregate and Structure 6
2.3 Effects of Petroleum Spill on the Environment 7
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2.3.1 Effect on Plants 7
2.3.2 Effects on the Geotechnical Properties of Soils 7
2.3.3 Effects on Sandy Soils 8
2.4 Concept of Bioremediation and History 9
2.4.1 Biological Process of Bioremediation 10
2.4.2 Petroleum Hydrocarbon Degrading Microorganisms 10
2.4.3 How Bacteria Functions and Adapt to Environmental Conditions 12
2.4.4 Bacteria Reproduction and Survival 13
2.5 Growth Cycle of Microorganisms and Reproduction 13
2.5.1 Lag Phase 13
2.5.2 Stationary Phase 13
2.5.3 Exponential and Declining Phase 14
2.5.4 Death Phase 14
2.5.5 Kinetics of Bacteria Growth 15
2.6 Factors Influencing Hydrocarbon Metabolism on Bioremediation 15
2.6.1 Temperature and Chemical Composition of Crude Oil 16
2.6.2 Nutrients of Nitrogen and Phosphorus 16
2.6.3 Oxygen Requirement 17
2.6.4 Moisture Content and Surface Area 17
2.6.5 Soil pH 18
2.6.6 Organic Matter and Carbon 19
2.7 Techniques of Bioremediation 20
2.7.1 Bioaugmentation Process 20
2.7.2 Biostimulation Process 20
2.8 Importance and Advantages of Bioremediation 21
2.8.1 Disadvantages of Bioremediation 21
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CHAPTER THREE
3.0 Materials and Methods 22
3.1 Sample Collection 22
3.2 Experimental Procedures 23
3.2.1 Physical Parameters 23
3.3 Classification Test 24
3.3.1 Visual Description of Soil Colour and Structure 24
3.3.2 Sieve Analysis 24
3.3.3 Soil pH in Distilled Water 25
3.3.4 Total Hydrocarbon Content 25
3.3.5 Available Nitrogen Using H2O2/KCL Extraction 25
3.3.6 Available Phosphorus 25
3.3.7 Total Organic Carbon 26
3.3.8 Total Heterotrophic Bacteria Counts 26
3.3.9 Total Heterotrophic Fungi Count 26
3.3.10 Statistical Analysis 26
3.4 Equations for the Calculations of Parameters 26
3.4.1 Moisture Content 26
3.4.2 Particle Size Distribution 27
3.4.3 Soil pH in Water 27
3.4.4 Total Hydrocarbon Content 27
3.4.5 Total Organic Carbon Content 28
3.4.6 Available Phosphorus 28
3.4.7 Available Nitrogen 28
3.4.8 Total Heterotrophic Bacteria and Fungi Count 28
3.5 Statistical Analysis 29
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CHAPTER FOUR
4.0 Result and Discussion 30
4.1 Particle Size Distribution Parameters 30
4.2 Moisture Content 30
4.3 Total Hydrocarbon Content 31
4.4 Total Organic Carbon 31
4.5 Soil pH 31
4.6 Available Nitrogen 32
4.7 Available Phosphorus 32
4.8 Total Heterotrophic Bacteria and Fungi Count 32
4.9 Graphs 34
CHAPTER FIVE
5.0 Conclusion 46
5.1 Recommendation 46
REFERENCES 48
APPENDICES 53
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
In Nigeria, particularly in the Niger Delta regions; the soils found are mostly sandy soils in
shades of different colours of white, brown, grey and red. Sands are cohessionless aggregate
of rounded, subangular or angular fragments of more or less unaltered rock or mineral
particles of size from 0.075 -4.75mm (Murthy,2009). The sand separates recognized are: very
coarse, coarse medium, fine and very fine determined from the particle size distribution
curve. The coefficient of uniformity which is an index value showing the average slope of
grain size distribution in a soil depends on the gradation or distribution curve of the soil
sample. According to Arora (2008), the larger the numerical value of coefficient of
uniformity, the more the range of particles. Sand particles because of their size have a direct
impact on the porosity of the soil.
The high incidence and frequency of crude oil spill have been of great concern to
Environmental Engineers in Nigeria. This has given rise to intensive research to find ways
and means of generating information and data required to assist in bioremediation strategies
of crude oil spills.
Before any remediation strategy can be done successfully, a lot of information would be
required to aid the process (Bidemi, 2011). This information is meant to assist in the
detection of and response to oil spill incidence.
Bioremediation is a means of cleaning up contaminated environments by exploiting the
diverse metabolic abilities of microorganisms to convert contaminants to harmless products
by mineralization, generation of carbon (IV) oxide and water, or by conversion into microbial
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biomass (Baggott, 1993; Mentzer and Ebere, 1996). In Nigeria, no information is yet
available regarding the commercial production of fungi or microbial inocula for use in
bioremediation of oil polluted environments.
The effectiveness of bioremediation is dependent upon physical and chemical condition as
well as correct analysis of the parent microbial population and environmental condition
(Nedwell, 1999). It has been found that oil is degraded efficiently by oil oxidizing
microorganism under laboratory and field condition (Grondeva et al., 1993). To enhance the
natural cleaning action, special fertilizer which contains nutrients of nitrogen, phosphorus and
potassium (NPK 15:15:15 fertilizer) is applied to the polluted site. Bioaugmentation process
of bioremediation may not be effective for use in oil spill cleanup situation because the
addition of non native organisms will often cause competition with the existing beneficial
microorganisms (Zhu, etal., 2001).
Some of the naturally occurring microbes capable of degrading petroleum hydrocarbon are
Pseudomonas, achrombacter, arthrobacter, bacillus, flavobacter, nocardia, vibrio,
connybacterium, alcaligeu (all are bacteria organism).Yeast and fungi organisms are
Aspergilium, candida, cladspotum, penicillum, rhodomia, trichodermia (Zhu, et al., 2001).
Analysis of biodegradation rate of crude oil contaminated soil using fertilizer or cow dung
showed that fertilizer was a better nutrient source for biostimulation than cow dung
(Obahiagbon and Audu 2000). Numerous laboratory studies on nutrient enhancement of oil
degradation by natural occurring microorganism have concluded that, this technique is
promising for use in stimulating oil degradation (Amanchukwu etal., 1989, Pitchard and
Coastal 1991, Oliver etal, 1978). Excessive application of the fertilizer can lead to
accumulation of nutrients in the soil. The uncertainty about the toxicity of various fertilizer
formulations and microbial products inhibit broader use of bioremediation on marine
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shorelines (Hoff, 1993). Field application of nutrients is influenced by temperature, water
runoff, substrate and other environmental parameters that are neither fully understood nor
easily quantified (Atlas, 1995).
The 1990 Gulf of Mexico spills clearly showed that bioremediation could not be measured in
minutes or hours but over a period of days and weeks (Hoff, etal., 1993). The Puerto Rico
spill of 1994 clearly showed that at warmer temperatures, bioremediation generally takes 6
weeks while at cooler temperature it spans to several months. This simply implies that
bioremediation is not a fast process but a slow process. It has been found that addition of
certain nutrients and microorganisms to crude oil contaminated soils fastens the rate of
hydrocarbon loss a process called bioremediation. Obahiagbon and Audu( 2000) in their
various researches have carried out extensive study of biodegradation rate of crude oil
contaminated soil using fertilizer or cow dung and observed that, fertilizer was a better
nutrient source for biostimulation than cow dung. Ayotamuno and Kogbara(2006) in their
study found out that, crude oil contamination of agricultural soils limits the availability of
oxygen in the soil layers and hence impedes the biodegradation process but they failed to
investigate on the particle sizes of the soil layers to detect the porosity and voids.
Other notable researchers have also carried out studies on the physiochemical and microbial
characteristic of various soils, but not much has been done on the effects of particle size on
bioremediation. With this as the study background, the physical properties, chemical and
microbial characteristics of the soil samples were used in the assessment of the rate of
Hydrocarbon loss at the end of remediation.
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1.2 STATEMENT OF PROBLEM
There are very few information about the soil particle size properties on bioremediation.
Therefore, this research is aimed at investigating on the effects of particle size distribution
parameters like; effective size diameter (d10), coefficient of uniformity (Cu) and average grain
size (d50) as well as chemical and microbial properties of different sandy soils and their
effects on bioremediation
1.3 SIGNIFICANCE OF STUDY
Since bioremediation process of cleaning up oil spills has proven to be an effective method
but a slow process, this study is considered very important as it provides information and data
about the particle sizes of sandy soils (Cu and D50) on bioremediation. Through intensive
laboratory analysis, data generated will be used as reference tool for further research on
bioremediation, academic guide to students, Engineers, contractors and consultants who wish
to embark on a similar project.
Statistical Method using regression analysis was used at the end of the research to show the
linear relationship and correlation coefficient of the parameters with time in days.
1.4 OBJECTIVE OF STUDY
The objectives of the study is summarised thus:
· Compare the effects of particle size distribution parameters (Cu and D50) on
bioremediation, characterise the soil and crude oil samples used for the experiment.
· To determine the soil Physiochemical and microbial characteristics and their effects
on bioremediation.
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· Make comparison and discuss bioremediation results of soil samples with past related
projects.
1.5 SCOPE OF STUDY
1) Review of past literature on similar project
2) Sample collection and locations
3) Contamination of different sandy soil samples with crude oil at a uniform concentration of
4% each.
4) Laboratory analysis on Physical, Chemical and Microbial properties of the Soil samples.
5) Combined practice of bioaugmentation and biostimulation process of remediation
respectively.
6) Weekly soil sampling for laboratory analysis (0-7) days for a period of 42days.
7) Presentation and comparison of results with past related projects.
1.6 LIMITATION
Due to the different locations where the samples were got from, large quantity of disturbed
sandy soil samples required for the experimental work, were transported to the Civil
Engineering Laboratory of the University of Nigeria, Nsukka, this was tedious and expensive.
The non availability of required equipment, reagent and apparatus for the chemical and
microbial analysis of the soil resorted to; conducting the test in a Standard Laboratory
(Search Gate Laboratory Lagos, Soil Science and Microbiology Department UNN) which
was capital intensive and tedious. Preserving and transporting the samples particularly during
weekly sampling for 42days was tedious.
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