ABSTRACT
Model studies of groundwater quality and formation characteristics in phreatic aquifer were carried out in Rivers State the study area. The research was to find a better solution of pollution transport in groundwater, considering the effect of geologic parameters such as heavy metals, micronutrients, porosity, permeability, and void ratio. The source of pollution was through indiscriminate dumping of biological wastes and wastes from soakaway, regenerating the wastes in most parts of the study area. This research was carried out through an experiment performed for E.coli transport, including some other parameters that influence microbial growth, inhibition and variation for fast migration within a short period of time. These parameters are heavy metals, micronutrients, permeability, porosity, and void ratio. Velocity of solute transport (E.coli) was determined through column experiment in each soil sample for all the locations. Empirical model was applied through experimental results plotted, generating a polynomial equation. The expressions from polynomial were applied to verify the results for E.coli, micronutrients, heavy metals, degree of porosity, permeability and void ratio. The physiochemical parameter from the study carried out found that the growth of E.coli under environmental conditions favoured it. The research was able to produce the level of physiochemical parameter influencing E.coli concentration in groundwater. The presence of E.coli depends on the availability of nutrients as well as favourable conditions in terms of physiochemical parameter. More so, the concentration increased with depth in micronutrient. The study confirmed that the higher the depth of water, the lower the population of E.coli in some locations based on the decrease in substrate utilization; while in some areas, it varies. The study explained that the rapid growth on the population of E.coli is experienced when the pH value is acidic than alkaline. The study carried out was able to express the stabilization of groundwater quality by inhibiting the presence of metallic element in some locations; while in few locations in the study area, it was discovered that the presence of E.coli in different aquifers have lower percentage and become less harmful to the quality of groundwater for human utilization. The level of porosity were investigated on the migration of E.coli influenced by porosity from one aquifer to the other, the results were calibrated and verified generating a model that can be applied to predict the rate at which E.coli transport within a short period of time. The variation of micropores i.e. void ratio from different soil depositions were determined, calibrated and verified. The results can be applied to predict the variations in the micropores and hydraulic conductivity within the soil structure, as it influences the variation in the migration of E.coli in phreatic aquifers. The rate of liquid flow within the soil profile (stratum) i.e. through the rate of permeability, is imperative because it has contributed to the rate of distribution of E.coli, as well as effectiveness in terms of stability in the region by reducing the migration and transport at different strata, this was investigated in the study. The results on the level of flow and the influence on the permeability were determined in the study areas. The permeability results were verified to predict the rate of velocity of water like that of solute at different soil formations, this results verified can be applied to predict the velocity of ground water influencing the rate of transport at different strata, the verified model result can be applied to predict the time at which the microbes can transport to groundwater aquifers in all the study areas. The soil compositions influenced by E.coli concentration as well as the rates of migration were investigated, the soil profile that contains high concentration known to be gravel and coarse were determined. Finally, the developed model from experimental results should be applied by thorough assessment of the area, to determine the type of concept to be applied in assessment of ground water quality in the study location through design of boreholes.
TABLE OF CONTENTS
CHAPTER 1: INTRODUCTION
1.1 Background of the study 1
1.2 Transport influence and Geologic History of Rivers State 6
1.3 Statement of Problem 10
1.4 Objectives of the Study 11
1.5 Scope of the Study 13
CHAPTER 2: LITERATURE REVIEW
2.1 Darcy’s Law 15
2.1.2 Transport Processes 15
2.1.3 Molecular Diffusion 17
2.1.4 Mechanical Dispersion 18
2.1.5 Advective Dispersive Equation (ADE) 19
2.1.6 Degradation 19
2.2 Determining Straining of Escherichia coli from Breakthrough Curve 21
2.2.1 Pore size Density Function 29
2.2.2 Bacteria Transport Model 30
2.2.3 Determining the Van Genuehten Parameters 32
2.2.4 Tracer Breakthrough 33
2.2.5 E.coli Breakthrough 33
2.2.6 Volume available for Straining 36
2.2.7 Indicator Organisms 43
2.2.8 Morphology and Surface Characteristics of E.coli Taxonomy 46
2.3 E.coli in Water 48
2.3.1 Hydrophilic Bacterial Cell Wall 50
2.3.2 The Surface Charge of E.coli 52
2.3.3 Non-uniform Surface charge Distribution 53
2.3.4 General Bacteria Transport Model 55
2.3.5 Simplifying the rate expression for fractional surface coverage
(Eqn. 2.36) for E.coli Transport 60
2.3.6 Blocking 61
2.3.7 The Attachment Rate Coefficient 62
2.3.8 The Single Collector Contact Efficiency (h0) 64
2.3.9 The Straining Rate Coefficient 65
2.4 Relative Importance of the Bacteria Transport Mechanisms 68
2.4.1 The Filter Coefficient (β) 69
2.4.2 Factors Affecting the Contact Efficiencies 70
2.3.3 Effect of Grain Size Uniformity of Sediment 71
2.4.4 Factors Affecting the Collision Efficiency 72
2.4.5 Effect of Ionic Strength 75
2.4.6 Effect of Lipopolysaccharides Composition in the outer Membrane 76
2.4.7 Effect of Geochemical Heterogeneity 77
2.4.8 Effect of Grain Surface Roughness 79
2.4.9 Evidence of Bimodal Efficiencies 79
2.4.10 Filter Coefficients and Collision Efficiencies from Field
and Laboratory Experiments 82
2.5 Kinetic Desorption or Detachment 85
2.5.1 Factors Affecting Inactivation 86
2.5.2 Effect of protozoa and antagonists 87
2.5.3 Other effects on the die-off rate coefficient 88
2.6 Measuring and Modeling Straining of Escherichia coli in
Saturated Porous Media 96
2.6.1 Theory 99
2.6.3 Model Fitting and Numerical Modeling Tools 101
2.6.4 Electrokinetic Characterization of E.coli, Cell Size
and Stability of the E.coli Suspension 103
2.6.5 Nature and Occurrence of Straining, Attachment and Detachment 104
2.6.6 Model Fitting 107
2.7 Sensitivity of the Model Results to Parameter Values 109
2.7.1 Comparing Modelled and Measured Values 110
2.7.2 Effect of Transport Distance 112
2.7.3 The fitting parameter B and the mass balance of strained bacteria 134
2.8 Transport of E. coli in Columns of Geochemically Heterogeneous Sediment 120
2.8.1 Porosity of the column sediments 125
2.8.2 Column experiment method 126
2.8.3 The result conditions during the experiments 127
| Fig 2.18: |
2.8.4 The breakthrough curves 127
2.8.5 Sticking efficiency 128
2.8.6 Effects of Lag and Maximum Growth in Contaminant
Transport and Biodegradation Modeling 132
| Source: Taylor & Francis, 2007). |
2.8.7 Description of kinetics 133
2.9 Modeling Solute Transport in Porous Media 140
2.10 Virus Transport from Septic Tank Systems near Seasonally
Inundated Areas through Shallow Aquifers 151
2.11 Factors Affecting Microbial Survival in Groundwater 160
2.12 Studies on Viruses 164
2.12.1 Studies on Viruses and Bacteria 171
2.12.2 Studies on Bacteria and Cryptosporidium 174
2.13 Comparison of Escherichia coli and Campylobacter Jejuni
Transport in Saturated Porous Media 178
2.14 Survival of Water Quality Indicator Microorganisms in the
Groundwater Environment Temperature and Total
Dissolved Solids Effects 189
2.14.1 Biomass Structures in Porous Media 196
2.14.2 Microbial Attachment/Detachment Processes in Porous Media 199
2.14.3 Modeling Biological Reactions in Porous Media 212
2.14.4 Heterogeneity, Transport, and Scaling Issues 215
2.15 Solute Transport Models 222
2.15.1 Deterministic-functional models 223
2.15.2 Stochastic-mechanistic models 223
2.15.3 Stochastic-functional models 225
2.15.4 Deterministic-mechanistic models 226
2.15.5 Solute Transport Models for Multi-Layered Porous Media 228
2.15.6 Solution of Governing Equations for Transport Models 231
2.15.7 Parameter Estimation 236
2.15.8 Modeling of Solute Dispersion 236
2.15.9 Models for Solute Dispersion at various Scales 238
2.15.10 Deficiency of Previous Researchers 244
CHAPTER 3: METHODOLOGY
3.0 Theoretical Background 248
3.1 Experimental Method 250
3.2 Permeability Test 250
3.3 Physiochemical Analysis of Heavy Metals and Micro Elements 252
3.4 Column Experiments 252
3.4. 1 Experiment set up 252
3.5 Bacteriological Testing of Water 253
3.5.1 Choice of Technique 253
CHAPTER 4: RESULTS AND DISCUSSION
4.0 Data Analysis 256
4.1 Concentration of Micronutrients versus Depths at Different
Locations 259
4.2 Concentration of Heavy Metals versus Depth at different Locations 270
4.3 Concentration Result of Micronutrients at Upland Location 296
4.4 Concentration of Column Experiment at Different Depths 314
4.5 Concentrations of Heavy Metal, and Micronutrients at Different
depths in Coastal Locations 331
4.6 Concentration Micronutrients at different Depths and Locations 335
4.7 Concentrations of E.coli at different Depths and Locations 339
4.8 Model Verification for Permeability, Porosity and Void Ratio
Experimental Result 343
4.9 Calculated and Measured Values of Porosity at Different
Depths and locations 364
4.10 Calculated and measured Model Values for Void ratio at
Different Depths and Locations 386
4.11 Determined Coefficient of Permeability Result and Discussion 407
4.12 Verified model result for E.coli, micronutrient and heavy metals 424
4.12.1 Model Result from Column Experiment (E. coli) 424
4.12.2 Calculated and Measured Values of E. coli transport 434
4.12.3 Calculated and Measured Values for Heavy at Different depths 454
4.13 Calculated and Measured values Micronutrients at different
depths and Locations 474
4.14 Velocity of Micro organism (E.coli) transport from Column
Experiment at Different Locations 494
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 513
5.2 Recommendations 524
5.3 Further study 525
References 526
Appendices
CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
Throughout history, the quality and quantity of drinking water has been the major concern and the most vital issue in human welfare on earth today. The quality and quantity of water valuable to human have disappeared because of water shortage resulting from changes in climate. Even temperature, fluctuation, and limited precipitation caused problems. Devastating drought in Africa in 1980 resulted in catastrophic crop failure and more so; water is the most abundant liquid on earth. It covers three quarters of the earth, and settlement hinges on the availability of water. In man, three quarters of the fluid in him are made up of water. A man can live about a month without food, but he will die in a week without water, hence experts claim that declining supplies of fresh water will be a source of increasing tension in coming years. Worldwide, more than one billion people do not have access to clean water. About thirty percent of groundwater consist of fresh water, most of which are inaccessible, unusable or may be obtainable at great expense of energy. Only three-tenth of one percent of total fresh water can be truly considered as renewable. The water from rainfall seeping into the soil to nourish plant and tree growth and lakes, flow into the ocean and evaporating into the atmosphere in a natural hydrological cycle that will produce more rain. In 2004, there were still at least one billion people across the world, which do not have access to safe drinking water. Many of these people live in rural areas and are among the poorest and more vulnerable to be found anywhere in the world.
The international community has set up ambitious millennium development goals, to reduce by half the number of people without clean water by 2015. In this context the need for sustainable development and management of groundwater cannot be overstated. Across large swathes of Africa, South America, and Asia, groundwater provides the realistic water supply option for meeting dispersed rural demand. Alternative water resources can be unreliable and expensive to develop, surface water (if available) is prone to contamination and often seasonal, and rainwater harvesting can be expensive and requires good rainfall throughout the year. Groundwater, however, can be found in most environments, if you look hard enough with the appropriate expertise. Groundwater is the portion of the earth water cycle that flows underground. Groundwater originates from the precipitation that percolates into the ground. Percolation is the flow of water through soil and porous/fracture rock. The water table separates the saturated, or aquifer zone from the unsaturated or vadose zone, where the water does not fill all the voids or space in the soil or rock. The general trend is for water in the unsaturated zone to move down water until it reaches the water table. On the other hand, water in the saturated zone moves primarily along horizontal hydraulic gradients, from high to lower elevation, the ocean is the natural sink for groundwater flows.
Groundwater does not recycle readily. Rate of groundwater turnover vary from days to years, and from centuries to millennia, depending on aquifer location, type, depth, properties, and connectivity. The average time for the renewal of groundwater is 1,400years. Shorter renewal times tend to be associated with shallow groundwater, while longer renewal times are associated with deep groundwater.
Groundwater flow occurs under conditions that are usually classified as being either confined or unconfined. Confined groundwater flow is vertically constructed by the local geology and characterized by having positive fluid pressure throughout the domain. Conversely, unconfined flow occurs where there is a transition flow, positive fluid pressures in the saturated part of the domain, across an interface called the phreatic surface where the fluid pressure is atmospheric, into the unsaturated zone where fluid pressures are negative due to capillary forces. Because there is an open continuum, between surface processes, both natural (e.g. recharge) and artificial (e.g. waste disposal), and subsurface flow processes under unconfined conditions, then it is imperative that unconfined flow processes can be quantified to aid in the understanding and management of stresses upon the resource. Figure 1.1 shows a schematic diagram of an unconfined aquifer and associated features such as the phreatic surface and recharge processes.
| L |
| H |
| Surface water |
| Unconfined aquifer |
| Surface water |
| Region where horizontal flow modeling is valid |
| Region where horizontal flowmodeling is invalid |
| Region where horizontal flowmodeling is invalid |
| Recharge |
Figure 1.1: Unconfined groundwater flow and associated processes at the regional scale.
This explains predominance of unconfined beds being recharged by high rain intensities. This increases the groundwater aquifers under the influence of deltaic aquifer as expressed in the figure. Technique of Seepage-face boundaries occur at the interface between an unconfined aquifer and a surface water body. The formation of seepage-face boundaries is caused by vertical flow components, which can dominate at the groundwater-surface interface and therefore cannot be detected through the use of models that invoke horizontal flow strategies.
Over the past decade, this recognition is in part, a response to the realization of how the ubiquitous nature of horizontal flow modeling has stifled the understanding of the complicated three-dimensional flow patterns in several studies in some regions. In a recent survey of hydrological research, experts identified coupled groundwater and surface water problems (under the umbrella of salt-water intrusion problems), as one of the five, groundwater related societal problems that are presently unresolved and cannot be reliably resolved using current scientific knowledge. Further, the importance of understanding unconfined flow and groundwater-surface water interaction has been highlighted, as an important point of interdisciplinary research. For example, previous expert presented a review, which linked a poor understanding of subsurface flow at the groundwater-surface water interface to a lack of understanding of water quality changes and nutrient cycling in the vicinity of the groundwater-surface water interface.
Therefore, given that a lack of understanding of unconfined groundwater flow simulation at the groundwater-surface water interface has been established, most previous studies has presented a largely theoretical development of various numerical modeling strategies able to simulate unconfined groundwater flow where vertical processes on solute transport and seepage-face formation were necessary. The model development is used to investigate several specific research objectives.
1.2 Transport Influence and Geologic History of Rivers State
Rivers State is part of the Niger Delta, which is at the Southern end of Nigeria bordering Atlantic ocean and extends from about Longitude 3’90E and Latitude 4’30-50 20N. Rivers State is part of the Niger Delta Environment that developed from the moto delta in the Northern part Basin during the companion transgression and ended with the Paleocene transgression. Rivers State formation is generated from the Niger Delta modern formation during the Eocene. It has three major depositions also just like every other part of the Deltaic Environment. Marine mixed and continental generally observed in the Deltaic Environment. The three major formations are Benin, Agbada and Akata formation; it was estimated that one million cubic meter of sand are carried towards mahin every year. While that of the Niger Benue are deposited on top of the Delta.
Since the study focuses on the Benin formation i.e. groundwater disintegrating to sombrero that transit at the Ahoada River, the geologic history of Rivers State are predominated by the deposited formation. The stratigraphy of the study area (Rivers State) are deposited by locustrine, Alluvial and fluvovia including off lap sediments, The locustrine deposit in the study area is heterogeneous predominant while alluvial and fluvovia deposits are homogenous predominant. Its coastal area on the study is where off lap sediments including tidal channels of 60ft and 800ft deep.
More so, the fluvovia has marine deposits that include clay upward changing to laminated clay silt and fine sand. The fluviomarine character gradually becomes more pronounced, the sand thickens, and the grain size increase and plant remains become more prominent. While the fluviotile deposits are best followed from inland to the coast, the sediments are characteristically finer upward and the width thickness ration is of order of 400-800 far the point bars, thus distinguishing them from tidal channel deposits.
This implies that there will be variations on the stratigraphy in the study area and will definitely influence the transport base these conditions. The deposited formation were confirmed to be the highest yield formation from a phreatic aquifer deposited, in every part of Rivers State, predominantly 90% of sand stone and 5% of sand stone and sedimentary deposited, it also has a predominant of montmonorite clay mineral including some other locations of deposited some hazardous chemical from manmade activities and natural origin. Its water table base on the study has an average of 7.5m water table. But in most coastal environment, it has an average of 1.5m water table.
The study also confirms that a good aquiferous zone has an average of 30-36m in the upland area while in the coastal area is 12-15metres. Porosity of the soil was confirmed to be very high which makes the focus of the study imperative for pollution transport, as abstraction of groundwater of good quality is complex due to its high level of variation in depth of formation for quality water. More so, some deposited physiochemical parameters are also confirmed to be deposited on some part of Rivers state, the deposition has the man made activities influence including the natural origin.
More so, in general, aquifer passage reduces pathogenic microorganism concentration and numerous successes have been reported in cases like artificial recharge schemes or riverbank filtration project, where microorganisms were completely removed. In Rivers State this is a serious problem; over sixty percent of the water abstracted from the ground is polluted water, because of inadequate implementation of design and application of standard in other to prevent these pollution threats of human life. However, studies in the USA have shown that up to half of all US drinking water well tested had evidence of fecal contamination and an estimated 750,000 to 5.9 million illnesses and 1400-9400 deaths per year may result from contaminated groundwater.
World Health Organization reports that in Africa around 80% of the population in the largest cities (in Asia around 55% have on site sanitation, such as septic tanks, pour-flush, VIP latrines or samples pits and experts say in developing countries in Asia, South American and African for an estimated one billion persons living in urban area, the main source of drinking water is groundwater.
Certainly, E. coli is one of the major bacterial that play major role in all the subject areas associated with the environment e.g. soil, air, and water. Many water borne diseases are caused by pathogenic bacteria, and it is the major task of water treatment.
Bacteria like E. coli, which normally lives in the intestine of warm blooded animals and are excreted with faces, are used as indicator bacteria. If present in water sample, they indicate that a contamination of water has taken place, and thus the potential presence of pathogenic exists. E. coli is the parameter tested, as an indicator of the presence of fecal bacteria and perhaps virus which pose a significant risk to human health. The most common health problem arising from the presence of fecal bacteria in groundwater is diarrhea, but typhoid fever, infectious hepatitis and gastrointestinal infections can also occur. Although E. coli bacterial are an excellent indicator of pollution, they can come from different sources e.g. septic tank effluence, farmyard waste, and landfill sites.
The published data about the elimination of bacteria and viruses in groundwater has been compiled by experts who show that in different investigations, 99.9 percent elimination of E.coli occurred after 16 to 120 days with a mean of 35 days for polio-hepatitis and entero-viruses. The natural environment, in particular the soil and subsoil is effective in moving bacteria and viruses by prediction filtration and absorption. There are two high-risk situations: Where permeable sand and gravel with shallow water are present and where fracture rock, particularly limestone is present close to the ground surface. The slow pace of the migration is where there are deposition of clay, which hinders the migration of the microbes, although preferential flow path, such as crack in the clay like mineral, can allow rapid movement, and by passing of the subsoil.
1.3 Statement of Problem
Rivers State, the study area of this dissertation being an industrialized state has high increase of population generating waste at a very high rate; precisely E.coli is part of this waste generation. It becomes imperative that such issue under study should be addressed with thorough research and some better solution to prevent the spread of diseases emanating from E.coli through groundwater contaminant should be generated.
The area under study has very high porosity based on hydrogeological studies, thus facilitating the transport of micro organisms especially E.coli. This usually leads to a high level of groundwater contamination leading to the breakdown of public health. Public health is a serious concern, because health is wealth. The behaviour of man’s activities has also attributed to the condition of pollution generated from our environment. Therefore, it is imperative that the cause of these problems emanating from manmade activity should be thoroughly examined in other to find better solution to prevent these problems and increase the health status of the citizens, as it is part of our economic development.
1.4 Objectives of the Study
Public health is an area of great concern due to the pollution level emanating from E. coli, through the transport source in the study area, since health is wealth, it should be thoroughly examined in other to see how the transport disperse to the aquiferous zone. A previous study was carried out on construction materials, abstraction of groundwater, and the way pollution is generated through the application of construction methods, precisely in Rivers State. These were as a result of application of substandard materials in design criteria and construction method. But the area of transport of E. coli was not carried out because it was above the scope of the study. Based on the limited scope, it becomes necessary that further studies should be carried out to cover a large part of the Rivers State environment; by analytically selecting the most affected locations for the study, the most affected areas can be used as a determinant for every part of Rivers state environment.
The serious effect of these pollution transports from E.coli, how it affect human is a serious disaster to human body. In this context, E.coli multiplies within the human digestive tract, producing a potent toxin that damages cells of the intestine lining. These lesions permit blood to rise to the bloody diarrhea, which generally develops within several days, eating contaminated food is one of the characteristic symptoms of infection from these pathogens.
Water pollution is also caused by the presence of undesirable and hazardous materials, beyond certain limits. Based on these unhealthy elements from E. coli, the objective of this research will focus on the following:
- To investigate the transport of coli through homogenous porous aquifers with respect to depth of aquifer and initial concentration.
- To investigate the transport of coli through homogeneous and heterogeneous porous aquifer with respect to depth of aquifer and level of concentration.
- To evaluate the relative importance of E. coli transport, which include their process and occurrence in natural environment
- To determine the coefficient of permeability of selected aquifer in several locations in study of four years (i.e. from 2004-2010) from the well-log history.
- To critically analyze the geological history and its influence on the transport of coli in the study area.
- To generate model that will generate better solution based on the geological formation in the study area.
- To calibrate and verify the experimental result from E.coli concentration and other influence on transport which include heavy metals, micronutrients, porosity, permeability and void ratio.
- To determine the velocity of solute transport (coli) from each soil sample to ground water Aquifer.
- To make necessary recommendations to stakeholders.
1.5 Scope of the Study
The scope of this study covers some selected locations in Rivers State, these selected locations are based on the critical analysis survey of most area concentrations of easy level of transport, based on its level of porosity and geological formation, including its topography, this ascertain all levels of transport in the study area.
The result from these selected locations from the study area will generate a general determinant level or model of pollution prevention and transport level to aquiferous zones in every part of Rivers State.
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