In: Groundwater Contamination Editor: Anna L. Powell
ISBN: 978-1-53611-003-6 © 2017 Nova Science Publishers, Inc.
Chapter 4
GROUNDWATER CONTAMINATION : PERFORMANCE LIMITATIONS AND IMPACTS IN NIGER DELTA-NIGERIA Awajiogak A. Ujile* Associate Professor, Department of Chemical/Petro-Chemical and Petroleum Engineering, Rivers State University of Science and Technology, Port Harcourt, Nigeria
NOMENCLATURE C C1 Co Dx, Dy exp ln h Kd K l,K s
*
Conc. of the contaminant at time t, (for conservative transport model), mg/Ls Concentration of the contaminant at time t, with 1st order reaction (for non conservative transport model), mg/L Initial concentration of the contaminant mg/Ls Directional hydrodynamic dispersion coefficients, m2 / s exponent Natural logarithm Distance of flow moved by pollutant; m Distribution coefficient. First order decay rate in the liquid phase and soil respectively, 1/s
Corresponding Author Email:
[email protected];
[email protected].
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Awajiogak A. Ujile K l M R t Vx, Vy
Overall first order decay rate = Kl + Ks ρb Kd /, 1/s.. Characteristic linear dimension, m. Bulk mass transfer coefficient of pollutant in groundwater flow in x-y direction, m/s flow in x-y direction, m/s. Retardation factor = 1 + ρb Kd / . Process time, or time since the start of the simulation, s. Directional seepage velocity components, m/s
Greek Letter ρb
Effective porosity; porosity of aquifer bulk density of soil, kg/m3
INTRODUCTION The Niger Delta is one of the largest wetlands in the world and produces crude oil, which accounts for about 85% of the total Nigerian government’s revenue. The states within the region are as follows: Edo, Delta, Bayelsa, Rivers, Akwa Ibom, Ondo and Cross River States. The two major rivers in Nigeria are the Niger River and the Benue River. The Niger River deposits all loadings from upper Niger at the deltaic zones. It meanders around 130 km south (Asaba, from Figure 1) of the apex into the Nun and Forcados Rivers. The formation of the Niger Delta can be attributed to a structural geological development, the interaction of the river discharges and its considerable sediment load towards coastal distributive forces, including the tidal currents in the outlets, ocean current and waves in the coastal area and the littoral drift. Perpetuation of these distributive forces (each with its own frequency) versus river discharges and sediment supply has led to building the Delta out into ocean (NDES, 1998). The Niger Delta is characterized by a network of rivers and creeks which drain the hinterland, transporting both water and sediments to the Atlantic Ocean. This process has created an extensive sedimentary region, roughly 30,000 km2 in area and populated by roughly 35 million inhabitants. The area is also rich in hydrocarbon resources, accounting for over 90% of Nigeria’s GDP. The difficulty of physical infrastructural development was foretold by the British colonial government (Willink Minorities Commission Report
Groundwater Contamination: Performance Limitations and Impacts … 67 (1957-58), who also advised the setting up of a special developmental commission, culminating in the creation of the NDDC (Abam, 2016). The impact of groundwater contamination in Yenagoa was considered in the region. Yenagoa is located east of the confluence of the Nun River and the Ekole River. The Niger Delta Environmental Survey Report, which was corroborated by the author (Ujile, 2003), asserted that the Niger River carries iron loadings from the deposits of the Itakpe Iron Ore and also through the processes of dispersion, advection, and inter-aquifer exchange, which move the pollutants to the groundwater aquifer. Ashim (1998) stated that most contaminants are detected some time after entering the subsurface; weeks, months, or years may pass before the problem is noticed. Contaminants may travel a great distance and affect a large portion of an aquifer before pollution is recognized. Ashim further stated that there are so many complexities involved in groundwater quality management issues; therefore, there is a need for impact evaluation as development progresses, with adaptation of the protection strategies, policy and management taken into consideration. This may be applicable to the issues of groundwater quality management in the Niger Delta. From the above standpoint, it becomes imperative to appraise the groundwater storage, geology, hydrogeology and aquifer systems, some pollutant distribution profiles, groundwater quality, model development and application of the model in the Niger Delta region. This chapter highlights these concepts, and makes recommendations to appropriate regulatory and governing bodies for implementation, control and management of groundwater resource for the region.
GROUNDWATER STORAGE Groundwater is stored under many types of geologic conditions. Areas where groundwater exists in sufficient quantities to supply wells or springs are called aquifers (water bearers). Aquifers store water in the spaces between the particles of sand, gravel, soil and rock, as well as cracks, pores, and channels in relatively solid rocks. An aquifer’s storage capacity is controlled largely by its porosity, or the relative amount of open space present to hold water. Its ability to transmit water (or permeability) is based in part on the size of these spaces and the extent to which they are connected USEPA (1996). If the aquifer is sandwiched between layers of relatively impermeable materials (clay), it is called a confined aquifer. Confined aquifers are
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frequently found at greater depths than unconfined aquifers. In contrast, unconfined aquifers are not sandwiched between these layers of relatively impermeable materials, and their upper boundaries are generally closer to the surface. It has been established (EPA Handbook (1994) that groundwater can move sideways as well as up and down. The groundwater movement is in response to gravity, differences in elevation, and fluctuations in pressure. However, the movement may be as slow as a few feet per year. In karst aquifers, the groundwater moves rapidly. These are areas in water soluble limestone and similar rocks where fractures or cracks have been widened by the action of the groundwater to form sink holes, tunnels or even caves.
GEOLOGY OF SOME PARTS IN NIGER DELTA The Niger Delta is dominated by the Benin formation and has been deemed as coastal plain sands (Ujile, 2001). Other formations observed in the region are the Agbada and Akata formations. Generalized stratigraphic successions are shown in Table 1, and the distribution of quaternary sediments is displayed in Figure 1. Table 1. Formation in part of Niger Delta (Adapted from Short and Stauble, 1964) Youngest known Age Recent Recent
Benin FM Agbada FM
Oldest known Age Oligocene Eocene
Recent
Akata FM
Eocene
Equivalent not known
Equivalent not known
Equivalent not known
Equivalent not known
Equivalent not known
Equivalent not known
Youngest known Age Plio/Pleistocene Benin FM M iocene OgwashiEocene Asaba FM ; Ameki FM Eocene IM O Shale Paleocene FM Nsukka FM M aestrichtian Ajali FM ; Companian M aniu FM ; Camp/M aest Nkporo FM Coniacian Awgu Santonian Shale Turonian Ezeaku FM Albian Aus River Group
Oldest known Age M iocene Oligocene Eocene Paleocene M aestrichtian M aestrichtian Campanian Santonian Turonian Turonian Albian
Groundwater Contamination: Performance Limitations and Impacts … 69
HYDROGEOLOGY AND AQUIFER SYSTEMS The main body of groundwater in major parts of the Niger Delta is contained in very thick and extensive sand and gravel aquifers of the Benin formation. The available borehole data shows three major aquiferous zones. These are the upper, middle and lower aquifer systems. Table 2 shows the characteristics of the various aquifers.
Figure 1. Distribution of Quaternary sediments in the Niger Delta (Abam, 2016).
Table 2. Characteristics of aquifers in Niger Delta Aquifer Upper
Depth (m) 18- 80
M iddle
30 -60
Lower
220-300
Characteristics M ost private boreholes derive their water here. Over-exploitation is noticed. Susceptible to saline intrusion Semi-confined zone. Consist of thick medium to coarse grained sand interfingered with thin clay lenses. Coarse grained sand and gravels with some clay interpolates.
Yield Low
M edium
High
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Within the mangrove swamps, the salinity level of water is high. It was reported that, since these areas are not protected from the dynamic zones of the deltaic front, it is possible for saline water to flow inland, creating a transition zone between fresh and saline waters. Fresh water extraction from swamps requires a borehole to be drilled to depths beyond 220 meters to avoid contaminated groundwater. Within sandbars and beaches of the coastal areas, boreholes have to go deeper to reach fresh water. The groundwater classification based on the geo-electrical sounding of some cities in the region are shown in Table 3. The results obtained from the geo-electrical sounding show complex configurations in the region. The three zones identified have shown that a fresh water zone just below the surface sand cover at 5 meters in a few locations can be misleading in choosing potable water. However, one should acknowledge the phenomenon of a mound as well in the region. Table 3. Groundwater Classification Based on Geo- Electrical Echo Sounding Tools NO COM M UNITY
1 2
Azuzuama Abalamabie
3 4 5 6 7
Bilabiri Ifoko (Bonny) Opume (Ogbia) Bomadi (Nun) Orukiri (Ekede Creek) Egbediama (Ekeremor LGA) Amaoku Bille Otuan (Yenagoa) Otakeme Peretorugbene Asarama - Toru Okoroba Ekeremor Okokokiri
8 9 10 11 12 13 14 15 16 17
Salt water contaminated zone (m) Surface-50 10-55
Ferrous Water Zone (m)
Fresh Water Zone (meters below ground surface)
117-200 55-70
5-75 8 -50 0 - 10 1 - 125
75-100 50 -150 35 - 190 30 -150 -
65-117 Surface sand cover 0-5 0-5 4-8 10 - 40 2 - 30 -
5 - 11
11 - 200
-
30 - 150 0 - 150 10 - 150 0 - 40 0 - 20 0 - 40
0 - 45 0 - 60 10 - 150 0 - 60 50 - 150 -
0.5 and possibly to 10 m 45 - 140 60 - 150 0 - 10 60 - 100 20 -50 40 - 150
Groundwater Contamination: Performance Limitations and Impacts … 71 NO COM M UNITY
18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
Torubia (Yenagoa) Orusangana Ayakoro Amakalakala Adagbabiri Ajagbene Ogbia Obonoma Abalama Ebedebiri Kolo I, II, III Okrika (Island) Otaboge Ikukiri (PJC/Isako) Agbegbene Okrika (M ainland) Anyama (Ogbia) Ngo (Andoni) Unyengala (Andoni) Krakrama (Akukutoru) Owupuku (New Calabar River) Sagbama Bukuma Forupa Koluama 1 Ekene Akassa Sangana Ikuru Kalaibiama Kala – kolo, Opukilo, Karama- Kolu
Salt water contaminated zone (m) -
Ferrous Water Zone (m)
Fresh Water Zone (meters below ground surface)
7 - 70
70 -150
1 -
20 - 48 5 - 60 10 -60 4 - 21 4 - 21 250 - 300 -
5 - 25 80 - 250
5 - 10 5 - 40 15 - 25
0 - 100 60 - 120 60 - 300 21 - 160 21 - 160 90 - 250 20 - 200 5 – 11 and possibly up to 35 5 - 150 10 - 150 55 - 150 40 - 150 25 - 75
5 - 120 75 -200 (mix)
75 - 200
0 – 2.5 0 - 75
5 -50 (mix) 5 -45 (mix)
2-9 5 - 50 5 - 45
9 - 150 50 - 80 45 - 80
25 - 75
175 - 200
75 - 175
2.5 - 150
-
-
5 – 120 9 - 50 20 – 80 20 – 125 7 – 100 5 -200 0 - 70
3 - 85 153 - 250
85 - 200 20 - 153
50 – 100
70 - 300 8 – 12
0-7 0-5 25 - 150
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Figure 2. Groundwater iron distribution map of Bayelsa and Rivers State in Niger Delta, (Ujile, 2013).
Contaminant Transfer in Groundwater Systems Mass transfer is the movement of any identifiable species from one spatial location to another. Chemical processes produce complex mixtures of compounds from various sources. Since separation processes are based on the creation of composition differences within and between phases, a consideration of mass transfer principles is necessary for the analysis and design of such processes (Ujile, 2003). Contaminated water flows into the ground from the surface of the Earth through pores in the soil and underlying geologic structures. Although these pores are very small and account for only a small portion of the underground volume, contaminated water moves very slowly underground and can cover large distances in depth (EPA Handbook, 1994). The quality of groundwater in some parts of the world, particularly shallow groundwater, is changing as a result of human activity. Groundwater is less susceptible to bacterial pollution than surface water because the soil and rocks, through which groundwater flows, filter out most of the bacteria. Bacteria, however, occasionally find their way into groundwater, sometimes in
Groundwater Contamination: Performance Limitations and Impacts … 73 dangerously high concentrations. But freedom from the bacterial pollution alone does not mean that the water is fit to drink. Many unseen dissolved mineral and organic constituents are present in groundwater in various concentrations. Most are harmless or even beneficial; though occurring infrequently, others are harmful, and a few may be highly toxic. The most common dissolved mineral substances are sodium, calcium, magnesium, potassium, chloride, bicarbonate, and sulphate. Facilitated transport, in which the mobility of a contaminant is increased relative to the expected retardation by adsorption to the subsurface solids, is a relatively new area of study in the field of contaminant transport groundwater systems (Ujile, 2007). Many researchers have studied the problem of solute movement through saturated porous media, both analytically and numerically. However, published literature related to a field problem on a regional scale such as the present one (the Niger Delta region) is scarce. Some examples of mass solute groundwater transfer include: the work of Mercer (1983) on modeling groundwater flow at the Love Canal; the modeled distribution of contaminants in an aquifer of glacial sediments by Bredehoeft and Pinder (1973); solute transport in limestone aquifer by Schwartz, et al. (1982); and assessment of the salt water encroachment phenomenon by Ashim, et al. (1982). Most of the investigations carried out by other researchers have not considered regional assessments with the application of second order differential equations. This work considered solute transport and a flow-model at a regional scale. Abraham (1976) used a single cell model to study the regional chloride and nitrate pollution pattern in a part of the coastal aquifer in Israel. Spanoudaki (2005) used the finite difference and orthogonal grids for Integrated Surface Water-Groundwater modeling. Shahld and Rahman (2004) applied a two-dimensional groundwater flow for the delineation of a wellhead protection area around the water well. Fatta, et al. (2000) carried out numerical simulations of flow and contaminant migration at a municipal landfill. Park, et al. (2002) applied transport modeling to the interpretation of a groundwater tracer. Other researchers have recently applied analytical methods for the mass transfer coefficient and concentration boundary layer thickness for dissolving non-aqueous phase liquid pool in porous media. It has been established that mass transfer occurs due to a concentration gradient or difference within a phase. A mass transfer rate between two phases is proportional to their interfacial area, and not the volumes of the phase present. A transfer owing to microscopic fluid motion or mixing is much more rapid than one due to molecular motion (diffusion) (Ujile, 2013).
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From the aforementioned standpoint, it becomes imperative to apply the solution of a second order partial differential equation that was established by the author (Ujile, 2003) to evaluate the mass transfer processes in groundwater contaminant flow models.
GROUNDWATER QUALITY IN THE NIGER DELTA – OVERVIEW The Niger Delta is an oil-producing region with saline and brackish mangrove swamps drained by a very dense network of creeks, where thousands of inhabitants travel several kilometers on local paddle canoes to get potable water. Waterborne diseases and airborne particulates are rampant in places like Ngo, Bonny, Okrika, Brass, Odioama and Nembe. Noxious particulate fallout substances have rendered the rainwater deleterious to health. Indeed, acid rain is experienced in the region. The mixture of seawater and freshwater of the Niger River during high tides render the water brackish and non-potable (Oteri and Atolagbe (2003). Despite the heavy annual rainfall of 3,000 mm in the Delta, and despite the numerous rivers that drain this region, the provision of potable water has been a major challenge over the years. Hence, potable water availability and supply are major problems amongst the various communities. In response to these threats, much attention has been devoted to groundwater development and exploitation since the mid-90s in this region. The increasing demand for potable water as a result of the recent population increase in the Niger Delta has called for the assessment of the sustainability of the existing water resources, particularly groundwater resource. In this case, the attempt to meet the water demand majorly with groundwater has called for critical groundwater research, especially in sustainable yield assessment. Groundwater is known to be an efficient perennial source of water and a much needed buffer during the times of drought (Calow et al., 1997). A resource can be locally developed for in situ utilization (Adepelumi et al., 2009). Groundwater is believed to be the ultimate source of potable water for the rural population due to its incremental development at an affordable cost and its relative stability than its surface counterpart (Carter, 2003). The mode of groundwater occurrence depends largely upon the type of formation, and hence upon the geology of the area (Garg, 1998). The possibility of in situ
Groundwater Contamination: Performance Limitations and Impacts … 75 development and utilization of groundwater makes it suitable for developing countries, particularly in Sub-Sahara Africa where there is limited financial capability to invest in large-scale infrastructure. Despite these positive and potential attributes, especially in the Sub-Saharan Africa context, groundwater’s advantage has not been fully taken (Carter, 1988); (Mutsa and Mark, 2007). Access to safe drinking water is generally inadequate in all of the states in the Niger Delta. This is a direct consequence of negligible water supply infrastructure, poor sanitation and waste management practices (NDES, 1998). The State Health Ministries estimate that just 20% to 24% of rural communities and 45% to 50% of urban communities have access to safe drinking water sources (MOH, Delta and Rivers, 1994). The estimates are corroborated by a survey of the general household, which found that all rural respondents in the Rivers State obtained their drinking water from streams, which have a higher risk of contamination than groundwater sources. Similarly, in the Delta State respondents in the riverine areas used surface water, while upland citizens tended to rely on boreholes (MOW Delta State, 1994). In the Niger Delta, water quality is not easily assessed because of very limited data. Bacteriological tests are not performed at the consumer level, but some measurements indicate the presence of coliform bacteria in tap water and from borehole analyses. Coliform and other bacteria indicate fecal contamination; they also have been found in surface waters, in locations in parts of the region. Borehole water characterization at the Ughelli Quality Control Center (UQCC) Camp site, Delta State carried out on 6/30/2003 gave results of fecal coliform (E. coli/100 ml) of 9 x 1013 E.coli/100 ml (Ujile, 2003). Table 4 shows borehole water 35 meters away from a dumpsite containing E. coli bacteria, chromium and lead contaminants. The water quality of five wells was treated in a study conducted by Inyang (2004) in Ekpri, Nsukkara and in the Uyo, Akwa and Ibom States. The values of the sampled parameters from the wells could not meet WHO standards. However, physicochemical parameters such as hardness, total dissolved solids, and pH levels met the standards. This shows that water quality is best assessed through both the physico-chemical and bacteriological tests. The latter test can show the presence of Coliform bacteria from fecal contamination through failed septic tanks. Coliforms can manifest in various shapes and sizes. Some can be facultative, aerobic, anaerobic, rod-like, or spores, and they all have various effects on water. Acceptable water should not contain more than three coliform organisms in 100mls (Ukpong, 2011).
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Table 4. Leachate and Borehole water concentrations of some pollutants at Elekahia Housing Estate PH, dumpsite adjourning borehole water respectively (Ujile, et al. 2008) Leachate component
Concentration
E-coli bacte ria Lead Chromium
9.6 x106 cfu/ml
Borehole water (35m away from dumpsite) E-coli bacteria
50.9 mg/kg 24.5 mg/kg
Lead Chromium
concentration Remarks
10 colony/ 100 ml 2.86 1.24
Above WHO values ‘’ ‘’
Out of the 112 borehole analyses in some towns and villages in the Rivers and Bayelsa States, 42%, 8%, 10%, 77% and 54% of iron, chloride, salinity, hardness and pH respectively were found to be contaminated (Ujile, 2013). The Funiwa blowout of 1980 had adverse effects on groundwater at Fishtown in the Bayelsa State. An ecological investigation carried out 18 months later revealed extensive environmental degradation of the area (Oteri, 1981). Presently, there are high levels of oil/gas exploration and exploitation in the region where the economy of Nigeria depends on. The groundwater quality assessment carried out by Adesuyi, et al. (2015) on 20 boreholes in the Eliozu community of Port Harcourt has shown contamination of most of the parameters, like dissolved oxygen, biochemical oxygen demand, etc. Groundwater studies in some areas in the Rivers State have shown increased levels in Total Dissolved Solids (TDS), up to 2900 mg/l; there was a high hydrocarbon content, with oil and grease at 71 mg/l in 2006 compared to 1.8 mg/l recorded 17 years earlier (Ayotamuno and Kogbara, 2007). Amajor (1991) and Ujile (2001) had reported iron and chloride elevation as groundwater issues, and this was corroborated by Ophori et al. (2007). Similar problems as reflected in the Bayelsa, Delta and Akwa Ibom States have also been reported (Amangabara and Ejenma, 2012); (Edet, 2004); (Amadi et al., 2010). A study adopted vertical electrical resistivity in order to determine the aquifer systems of the Ndokwa Land in the Delta State, Nigeria (Oteri, 1984). The study identified two to four layers of aquifers, with the third and fourth being geoelectric layers of the Earth. These layers consist of medium to coarsegrained sand formations, which have resistivity values ranging from 300 Ohms to 1,500 Ohms and an average thickness of 35 meters. The study concluded that aquifers within the study area are mostly unconfined and are
Groundwater Contamination: Performance Limitations and Impacts … 77 very prone to overhead contamination. However, the study revealed that a sustainable water supply could be tapped between the depths of 30 meters and 45 meters below the ground’s surface within the study area. Vertical Electrical Sounding using Schlumberger configuration was adopted to delineate shallow aquifers in the coastal plain sands of the Okitipupa area in southwestern Nigeria (Omosuyi, 2008). The study delineated two distinct aquifers within the study area. The first aquifer is the shallow area (which in most cases is unconfined) that occurs between the depths of 5.8 meters and 61.5 meters below the ground’s surface. The second aquifer unit is the intermediate area (which is mostly confined) that occurs between the depths of 32.1 meters and 127.5 meters below the ground’s surface. The study showed that the aquifers are made up of medium-grained saturated sand with an average resistivity of 296.8 Ohms. The study concluded that the occurrence of aquitards above the aquifers of Ajagba, Aiyesan, Agbetu, Ilutitun, Igbotako and Erinji make the aquifers less vulnerable to near-surface contaminants than in Agbabu, Igbisin, Ugbo and Aboto, where aquifers are overlain by less resistive materials. Based on these studies, one can conclude that the geology and the occurrence of groundwater (hydrogeology) in various parts of Nigeria vary heterogeneously as a result of the differential geological and geomorphological histories of various landforms and their underlying rocks. In this regard, variability does exist in the nature of groundwater occurrence in terms of its quantity and characteristics. In response, this study is carefully designed to assess the sustainability and yield potential of boreholes within the study area. The specific objectives are to: examine the relationships among the identified borehole parameters; establish a relationship between the yield of boreholes and some target borehole parameters for the study area; examine the implication of the above objectives on groundwater development; and management in the Deltaic formation of Niger Delta (Akinwumiju and Orimoogunje,2013).
MECHANISMS OF GROUNDWATER CONTAMINATION Contaminant releases into groundwater can occur by design, by accident or through neglect. Most groundwater incidents involve substances released at or only slightly below the land’s surface. Consequently, most contaminant releases affect shallow groundwater initially. However, certain activities such as oil and gas exploration, deep well waste injection, and pumping of groundwater underlain by saltwater also tend to affect deep groundwater.
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Groundwater contamination can occur by infiltration, recharge from surface water, direct migration and inter-aquifer exchange (EPA 1994, Ujile, 2003, Ujile et al., 2013). In the saturated zone, contaminants in the leachate spread horizontally in the direction of the groundwater flow and vertically due to gravity (Freeze and Cherry, 1979).
CONTAMINANT TRANSPORT PROCESSES The extent to which a contaminant moves in groundwater depends on its behaviour in relation to various processes that encourage transport and other processes that serve to retard them. The shape and speed of contaminant plumes are determined by these processes and by factors relating to the aquifer materials, as well as characteristics of the contaminants. In a nutshell, three major processes govern the extent to which chemical constituents migrate in groundwater:
Advection: movement caused by the flow of groundwater Dispersion: movement caused by the irregular mixing of waters during advection Retardation: a principally chemical mechanisms that occur during advection
However, Ashim (1998) considered that non-reactive (conservative) dissolved contaminants in saturated porous media could be controlled by the following factors:
Advection (convection): a mechanism that causes contaminants to be transferred by the bulk motion of the groundwater Mechanical (or kinematic) dispersion: a process that involves mechanical mixing caused by pore-scale heterogeneity Molecular diffusion: a mechanism that causes the contaminant molecules or ions to move opposite the direction of concentration gradient. The random kinetic motion of the ions and/or molecules causes this movement
Groundwater Contamination: Performance Limitations and Impacts … 79 In this chapter, the combined effect of mechanical dispersion and molecular diffusion (otherwise known as hydrodynamic dispersion) is applied to determine the performance and impact of the groundwater flow processes. In the region, it was observed that reactive contaminants are prevalent. This could affect mass transfer through additional processes of adsorption, desorption, and chemical or biological reactions. Ashim, (1998) described these processes as follows:
Adsorption or desorption: processes that involve mass transfer of contaminants. Adsorption is the transfer of contaminants from the groundwater to the soil; desorption is the transfer of contaminants from the soil to the groundwater Chemical reactions: processes that involve mass transfer of contaminants caused by various chemical reactions (e.g., precipitation, dissolution, oxidation and reduction). For some contaminants, degradation is also an important process that requires characterization
These processes of adsorption-desorption and chemical reactions play important roles in controlling/monitoring the migration rate as well as concentration distributions of groundwater contaminants. They also tend to retard the rate of contaminant migration and act as mechanisms for concentration attenuation. Table 5 shows the data requirements for contamination characterization. The parameters include a geometric description of water-bearing formations, storage and transmissivity properties; a source and sink are needed as well. Some aquifer hydraulic parameters in some locations in the Rivers and Bayelsa States are shown in Table 5. Presently, the expansion and development of housing projects from government and house owners have increased the growth rate of boreholes development in the region. A high pumping rate brings about an increase in drawdown and has caused a salt water intrusion phenomena into the lower aquifer in parts of Port Harcourt (see Figure 4). Other cities in the region have similar geological characterization, e.g., in Warri Delta, Yenagoa, and the Bayelsa States, respectively.
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Awajiogak A. Ujile Table 5. Some Aquifer Hydraulic Parameters in Rivers State and Bayelsa State (Ujile, 2003)
S/N
Location
Aquifer
Depth (m)
Transmissivity (T) m2/sec
Storativity (S)
1. 2. 3. 4. 5. 6.
1 1 1 1 1 2
33 40 38 40 37 195
1.05 x 10-2 8.58 x 10-2 2.1 x 10-2 1.06 x 10-2 1.12 x 10-2 3.82 x 10-2
3.21 x 104 3.53 x 104 ---1.07 x 104
7
Bori Yenagoa Isiokpo Choba Omoku Nembe Port Harcourt, M oscow Rd.
Specific Capacity m3/hr/m 19.01 55.2 ---75.1
2
165
5.1 x 10-2
--
130.1
8. 9 10 11.
Port Harcourt, Elelenwo Eleme Akpajo Onne
2 4 4 5
151 302 300 300
8.79 x 10-2 11.3 x 10-2 7.18 x 10-2 4.14 x 10-2
-2.75 x 104 ---
128.7 139.7 130.00 130.1
Table 6. Data pertinent to prediction of groundwater flow (Bouwer et al. 1988) Physical Framework: Hydrogeological map showing areal extent and boundaries of aquifer
Topographical map showing surface water bodies Water table, bedrock configuration and saturated thickness map Hydraulic conductivities map showing aquifer and boundaries Hydraulic conductivity and specific storage map of confining bed Map showing variations in storage coefficient of aquifer Relation of stream and aquifer (hydraulic retention) Estimates of the parameters that comprise hydrodynamic dispersion Effective porosity distribution Information on natural (background) concentration distribution (water quality) in aquifer Estimates of fluid density variations and relationship of density to concentration
Groundwater Contamination: Performance Limitations and Impacts … 81 Table 6. (Continued) Stresses on Systems: Type and extent of recharge areas (irrigated areas recharge basins, recharge wells, impoundments, spills, tank leaks, etc.) Surface water diversions Groundwater pumpage (distributed in time and space) Stream flow distribution in time and space Precipitation and evapotranspiration Sources and strengths of pollutants Chemical-biological framework: Minerology of media matrix Organic content of media matrix Groundwater temperature Solute properties Major-ion chemistry Minor-ion chemistry Eh-pH environment Observable Responses: Water levels as function of time and position Areal and temporal distribution of water quality in aquifer Stream flow quality (distribution in time and space) Other Factors: Economic information about water supply Legal and administrative rules Environmental factors Planned changes in water and land use
CAUSES OF GROUNDWATER CONTAMINATION Activities that can cause groundwater contamination can be summarized as shown in Table 7.
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Table 7. Activities that cause groundwater contamination (Adapted from USEPA (2002) Guide Url http://www.epa.gov/safewater...) Potentiometric Level Ground Surface
Above Water Table
Below Water Table
Primary Source Infiltration of polluted surface water, land disposal of wastes, stock piles, dumps, sewage sludge disposal Septic tanks, cesspools and privies, holding ponds and lagoons, sanitary landfills, waste disposal in excavations underground storage Waste disposal in drainage wells and lands, underground storage
Secondary Source De-icing salt uses storage, animal feedlots, fertilizer pesticides, accidental spills, airborne pollutants Underground pipeline leakages, artificial recharges, sumps and dry wells, grave yards Exploratory wells, abandoned wells, water supply wells, groundwater withdrawal
The sources of groundwater contamination in the Niger Delta are both from natural and human activity. The Niger Delta Basin serves as the receptor of water and sediments generated upstream from the Niger and Benue catchment. Investigations carried out by Teme (2002) and Ujile (2007) revealed that excess water and sediments generated during annual floods are released through the distribution network of rivers, creeks, rivulets, and canals into the Atlantic Ocean. Ibadan is the second largest city in Nigeria, and it is a major commercial, industrial and administrative center. Open waste disposal sites have produced a negative effect on the quality of groundwater and soil. The data obtained from all of the studies from the four sites indicate the existence of pollution near the disposal sites. The closest well to the waste site showed higher contamination than the control sites. It was noticed by the investigators that groundwater contamination spread horizontally (Ujile, et al., 2012).
RESEARCH NEEDS There is a lack of understanding in many important physical processes and system dynamics in groundwater environments. Processes in the unsaturated zone – those associated with the flow of immiscible contaminants, coastal aquifers, salt water intrusion, and complex chemical interactions and phase changes have received little or no attention in the Niger Delta region.
Groundwater Contamination: Performance Limitations and Impacts … 83 Consequently, engineers, scientists, hydrogeologists and water resources ministries both in the state and federal governments have limited the ability to predict the effect of remediation on the fate and transport of a contaminant in an aquifer; the effect of changes in pesticide and fertilizer applications for crop yields, and the effect of salinity build up on crop losses and human health are also unpredictable to an extent. The initial need for research lies in understanding the physical and chemical processes taking place in different sub-surface environments, and in developing mathematical representations of these processes. A proper understanding of a system’s dynamics in place can bring about the formulation and application of management models. There is also the need to expand our understanding of the criteria by which alternative management programs should be judged, and the types of constraints that need to be applied to obtain the objective function of systems. Lack of understanding of the decision–making process was also considered by Asit (1991) to be one of the most critical issues in the application of models for environmental management in developing nations. We can apply the same assumption in the Niger Delta region. Active areas of research that would be beneficial to the region may include Geographic Information Systems (GIS); computer graphics; field testing of simulation– optimization methodologies, and interactive approaches among the stakeholders should be encouraged by the government, higher institutions, consultants, political groups, and environmental regulatory agencies. The components of an integrated approach to groundwater management in the region may be looked at in the perspective as shown in Figure 3. In Figure 3, eight entities which could play a major role in the water sector – particularly groundwater management and quality sustainability in the region – have been identified. Other global organizations like WHO, UNICEF, and UNESCO should consider the complexities of the geographical terrain, the network of river interconnectivities, rivulets, creeks, and the effects of the Atlantic Oceanic shores and come to the aid of the inhabitants of the region to solve groundwater problems. They can liaise with the eight entities shown in Figure 3.
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Industry
Agric Agurlticuurleture Oil exploitation, Oil Exploitation Exploration activities Exploration activities Public
Water Resources Ministry
Environmental Consultants;
Federal Ministry of Environment
Hydrogeologists
(States & Federal)
Educational and Research Institutions
Niger Delta Development Commission
Figure 3. Developed components of an integrated approach to groundwater management in the Niger Delta region.
Figure 4 shows the Shell Petroleum Development Company of Nigeria, Ltd. operations in the Niger Delta. The environmental impact assessment of the construction and installation of these oil and gas activities have shown that the groundwater as a resource has been affected tremendously. Oteri (1981) has shown that the oil spill of the Funiwa blowout in 1980 impacted the groundwater supply at Fishtown in the Bayelsa State. Crude oil spillages and petroleum product seepages from storage facilities contribute to groundwater pollution problems (Ujile, et al., 2008). These researchers at the same time revealed that poor and improper waste management systems have become a problem for groundwater aquifers. A mathematical model of leachate transfer
Groundwater Contamination: Performance Limitations and Impacts … 85 from a typical dump site at Elekahia, Port Harcourt has been presented, and average transfer rates were obtained as well (Ujile, et al.,2008). Other major oil and gas companies that operate in the region include Total Elf and the Nigerian Agip Oil Company. They have their network of pipelines transporting crude oil and natural gas within the region as well.
Figure 4. Shell Petroleum Development Company of Nigeria, Ltd. Operations in the Niger Delta.
SALTWATER INTRUSION A random survey carried out between 1995 and 1998 on the sodium chloride and chloride content of groundwater in coastal locations of Port Harcourt has shown variations from one borehole to the other. The chloride concentration was 250 mg/l on 7/10/1997. After the dredging works of the Amadi Creek towards the end of 1997 and the early part of 1998, the chloride concentration increased to 350 mg/l. However, the Amadi–Ama axis, which is east of the Creek, has not experienced any significant increase in the chloride levels of the groundwater system. The dredging works might have created fault zones, which are permeable and therefore enhance saltwater intrusion into the aquifer
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(Nwachukwu, 2001). Similar trends are observed in the Diobu and Moscow Road areas of the Port Harcourt metropolis. High chloride content has been noticed in boreholes within other coastal towns and villages in the region, especially mangrove swamps, sandy islands and estuaries. In Port Harcourt (as seen in Figure 5), high chloride contents are found in boreholes that have boundaries between coastal plain sands and mangrove swamps. In coastal islands, chloride content is variable depending on the depth of the borehole. In Bonny Island, a shallow well with a low chloride content of 5 mg/l, but a high iron content of 0.8 mg/l at a depth of 304 meters is present.
Figure 5. A bar chart showing variations of chloride in groundwater in coastal locations of Port Harcourt (Ujile, 2003).
Groundwater Contamination: Performance Limitations and Impacts … 87
Iron Concentration Profiles in the Niger Delta In many places, groundwater contains excessive amounts of iron. Iron causes reddish stains on plumbing fixtures and clothing. Like hardness, excessive iron content can be reduced by treatment (USGS). Presently, there is no engineered landfill in this region. As a result, the groundwater resource is exposed to contaminations. The source of high iron content in the region may be from the upcoming deposits from the river system distributions throughout the Niger Delta, which affect the groundwater by processes of diffusion, advection and convection. The investigation shows that the iron concentration level in groundwater in some cities within the Bayelsa State, like Yenagoa, Toru Ndoro, Toru Fani, and Ekeremor are peculiar. It has been observed that cities that are situated along the Niger River and its tributaries have iron content values in groundwater between 1.5 mg/l and 5 mg/l. The Niger River flowing through the Itakpe iron ore deposits might be carrying iron deposits. As this approaches the Niger Delta region with obstructions (retardation factors), the iron ores are deposited by sedimentation. Figure 2 shows the distribution map of iron in the region.
EFFORT TO REDUCE CONTAMINANT LEVELS Presently, the two methods being used to treat groundwater contaminants are:
Aeration Chlorination
Aeration is applied by the state government to reduce the concentration levels of iron to acceptable (WHO) standards. However, individual borehole owners apply ion exchange (through the adsorption process) for iron removal. The Niger Delta Development Commission (NDDC) water development projects in the region have adopted the ion exchange procedure, but the regulation, control and sustainability of the process is lacking. The chlorination process is adopted to remove fecal bacteria from groundwater resource by the state government. Few borehole owners use the
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UV-stabilizer technique. Poor sanitation practice and indiscriminate open defecation by citizens promote bacterial contamination. The Ministry of Water Resources should implement The Water Quality Policy (ACTS), and the state government in the region should consider the design and construction of engineered landfills in the region as a way to prevent seepage of leachate into groundwater.
MODEL DEVELOPMENT PROCEDURE Considering the movement of contaminants from solid waste landfills into the potable water aquifers beneath it is an example of a groundwater pollution process system. The motion of fluid through porous rock induced by pressure and gravity is of great practical importance. The field data obtained in the region shows variation in hydraulic conductivity in a different direction. Tables 3, 4, 5 and 6 show the characterization of groundwater contaminants systems. Table 7 shows the activities that cause groundwater contamination. These activities constitute complex processes in the region to identify a mode of pollutants’ entry into the groundwater bodies. It is in light of this that a model procedure becomes imperative to consider the process at a macroscale to integrate the entire region. The modeling study is an integral part of the investigation process related to groundwater development and management. Presently, models are being used extensively for synthesizing many factors involved in analyzing complex groundwater problems. Modeling processes can be obtained from the work of Ashim, (1998); Anderson and Woessner, (1992); Anderson, (1979); Asit, (1998); Bear and Verruijjt, (1990). Our approach in this chapter involves the collection of field data from State Water Boards, private companies involving in groundwater activities in the region, and hydrogeologists reports. The analysis of such reports yields a conceptual model, and this provides a hypothesis for how a system or process operates. The conceptual model is then translated into a mathematical model defined by a set of governing equations and boundary conditions that contain mathematical variables, parameters and constants. Once a mathematical model is formulated, the next step is to obtain a solution using one of two general approaches: the analytical approach and the numerical approach. Konikow (1981) stated that when the parameters, boundary conditions and grid dimensions of the generic mode are specified to represent a particular
Groundwater Contamination: Performance Limitations and Impacts … 89 geographic area, the resulting computer program becomes a site specific model. Considering hydro-dispersive transfer in three dimensions, contaminants move through layers and a number of processes are in operation (e.g., filtration, dilution, oxidation, biological decay, etc.); these can lessen the eventual impact of the pollutants once they finally reach the groundwater. The effectiveness of these processes is affected by both the distance between the groundwater and where the contaminants are introduced, and the amount of time it takes the pollutants to reach the groundwater. Taking the mass balance of these processes and considering seepage factors, kinetic functions, and contribution sources with retardation factors, Asit (1998) and Ujile (2003) obtained a general expression: C
Ci
C
Ci
C
C
C b S
Ks
Dy y Vy y z Dz z Vz z t CKl S b t x Dx x Vx x y
(1) Equation 1 has expressed the various mass transport processes that affect the transport of contaminants in the subsurface environment. These include advection, molecular diffusion, mechanical dispersion, biochemical transformations and interphase mass transfer. Equation 1 is similar to the theoretical analysis of algae growth rate of change in the Nun River surface water (Abowei, 1989). However, in his study and analysis of photosynthetic rate and optimum biomass growth, Abowei only considered the horizontal diffusion coefficient, reducing the three-dimensional equation to one. In the author’s work on modeling groundwater contaminants due to transient sources of pollutants (Ujile, 2003), a quantitative framework for synthesizing hydrogeological conditions with spatial and temporal trends of the system response was provided. The work has been able to establish the procedure and determine contaminant travel time to identified receptors. Equation 1 was reduced to a two-dimensional flow model with certain criteria and engineering assumptions. The following conditions have been considered in the Niger Delta region:
Groundwater source/sinks are more than one (e.g., dredging works, oil exploration/exploitation, injection well, River drains, and pumping rate activities are predominant)
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The direction of groundwater flow is obviously in two dimensions (e.g., radial flow to a well or a single aquifer with a relatively small vertical hydraulic head or contaminant concentration gradient) Sites/locations in which the aquifer has distinct variations in its hydraulic properties have been identified within the region Impacts of transverse dispersion have also been identified
Three-dimensional flow and transport models of a contaminant cannot be applied in the Niger Delta on a macroscopic scale presently due to the following reasons:
The detailed hydrogeological conditions are not well established The geo-electric-echo sounding carried out in some communities (Table 3) shows three broad types of groundwater: potable water, ferrous water and water contaminated with saline intrusion The characteristics of the aquifer in the region is simple; upper, middle and lower (Table 2). The coastal plain dominates the Niger Delta geological structure, and so there is no vertical movement of groundwater, except contaminant transport by rain percolation through layers of the rock matrix
We therefore consider the two-dimensional flow as most appropriate. However, the two-dimensional flow carried out by Sauty (1980) has some limitations. The field data obtained in the Niger Delta region shows that the direction of flow in the horizontal x and vertical y directions is larger than the transverse z direction. Besides, the field data shows a variation in hydraulic conductivity in different directions (Table 5). e.g.,
C C C x y z hence, Equation 1 is modified to the form:
(2)
Groundwater Contamination: Performance Limitations and Impacts … 91 Basic engineering assumptions considered are as follows: Movement of the solute is assumed to be in the plane of the horizontal and vertical section of the aquifer, and the porous medium is assumed to be anisotropic with respect to the dispersivity of the medium. The density and viscosity of groundwater is assumed to be constant. This is the case in most groundwater flow systems. The groundwater flow pattern is not altered by the presence of multiple contaminants in a solution. Aquifers with unconsolidated formation of sand and gravel are predominant in the Niger Delta region, and porosity is considered more or less uniform on a regional basis. (Range 0.33-0.45) The first order decay rate in the liquid phase is the same as in the soil (solid) phase, (e.g., KL = KS). The mass transfer coefficient of a pollutant is considered on a macroscopic scale. This is because of hydraulic conductivity and porosity, which create irregularities in the seepage velocity and, consequently, the additional mixing of the pollutant. A solution procedure for the second order partial differential equation, which describes the groundwater flow and solute transportation, was developed. A numerical method, which incorporates the Taylor Theorem using a grid system in conjunction with analytical Euler methods, was applied to solve the partial differential model equations in two-dimensional flows. The solution of the final model equation is:
CA C In o = KL (1
b
K L (1 In b Kd /)
Kd /) M
(1
b h
M h –
Kd /) .t
(4)
The advantage of this solution over other researchers work is that the solutions to second order partial differential equations given by other researchers contain other complex functions like Bessel functions, complementary error functions, Hantush Well functions and others. These have created difficulties for graduate students and researchers for numerical/ analytical evaluations of parameters in practice. The Dirac operators and non-
C C 2C 2C C Dx – V x + KC = R D Vy y 2 2 t x y x y
(3)
Compact surfaces by Stefan and Herman (2003) have posed complex conditions for researchers and graduates to solve partial differential equations.
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From the above standpoint, it becomes imperative to establish solutions to second order partial differential equations that will be simple to all practitioners and researchers. This solution, as shown in equation (4), considers the existing difficulty and contains only an exponential function, which is so simple that a hand calculator can solve it.
APPLICATION OF THE MODEL The application of the model was carried out with the MATHCAD software systems. The expression in the parenthesis – (1 + ρb Kd / ) is called the retardation factor. This expression determines the resistance of the contaminant to move through the groundwater aquifer. The analysis of the parameter’s effective porosity was based on the transient characterization and its effect on the groundwater flow systems. The MATHCAD program was developed from the solution of the model equation, and the results are shown on the computer printout as shown in Appendices A to B. The input data for Yenagoa based on the hydrogeological features are: Boundary Conditions 0 ≤ x ≤ 500 0 ≤ y ≤ 49.5 For h = 500m; a = (0.1 – 1.0); b = (0.009 – 0.099); Co = 4.5 mg/l (iron content). Other input data are shown in Appendix A, and the output data is indicated in Appendix B. The results obtained in the form of the matrix of function values, surface, bar and contour plots over specified horizontal and vertical ranges show rapid divergent when effective porosity is increased. For the conservation transport model, the following observations are made: A reduction in contaminant concentrations with an increase in porosity values provides primary lines of evidence for the natural attenuation of each contaminant. The contour plots provide secondary evidence for possible biodegradation of contaminants in a spatial trend analysis. These observations may be correct for conditions where there are spillages of chemicals, dumpsites of municipal and hazardous wastes. However, the high iron content and hardness levels detected in most groundwater of the
Groundwater Contamination: Performance Limitations and Impacts … 93 region – especially in Yenagoa – has been traced to the upcoming deposits from the Niger Delta river system distributions, which affect the groundwater by processes of diffusion, advection, convection via inter-aquifer exchange, direct migration, infiltration and groundwater/surface water interaction. Therefore, the source of the contamination seems to be natural. The attenuation and biodegradation phenomenon may not apply in this circumstance. For a non-conservative transport model, the following observations are made: An increase in contaminant concentrations with an increase in porosity values shows that natural attenuation may not be tenable. The alternative solution to the groundwater problem will be to analyze borehole samples, and the results determine the treatment method(s) to be applied to obtain potable water. For the non-conservative transport model, there is an increase in contaminant concentration as it moves from source to sink. The model equation has proved that the concentration levels of iron pollutants in groundwater depend on the distance from the source of pollution, the time it takes to travel, the processes of transfer and the regime of flow. The distribution map of iron concentration was considered for a comparison of the simulated model output. The MATHCAD graphical representations of C and C1 for Yenagoa compare the distribution of the contaminants. The value C on the printout shows the gradual penetration of the contaminant’s dissolved molecules into the groundwater when there is no reaction. A comparison with C1 shows the change owing to the reaction with a first order decay rate. As time elapses, the concentration profiles with a reaction take on a different shape and approach a limiting exponential profile for which reaction and diffusion are in step at each value of the boundary conditions. The profile remains steady because the rate of diffusion at each value of h, a, and b (which determine the y and x positions) is exactly equal to the total rate of reaction throughout the aquifer length (x) and depth (y). When these occur, there is no further decrease in the mass transfer rate of contaminants into the groundwater bodies. The print out result shows that at the x-direction, the concentration of the contaminant increases on the surface and decreases in the y-direction, perhaps owing to the adsorption processes in the rock matrix. The surface, bar and contour plots of C and C1 illustrate the spatial distribution of contaminants without reaction and with first order reaction, respectively.
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CONCLUSION This chapter has highlighted the causes and effects of groundwater in the Niger Delta region. Anthropogenic and natural causes have been the major impact of groundwater contamination in the region. Research needs and support from world organizations (WHO, UNICEF, UNESCO, UNDP etc.) are required to minimize the effects of groundwater contamination in this region. The solution to second order partial differential equations for groundwater flow has been obtained. The application of the model equation has provided results that are similar to other works carried out by other researchers with complex results. The variation of porosity values has caused significant changes in the concentration of groundwater contaminants. This analysis can be applied for the design of natural attenuation landfill for both municipal and industrial wastes. Materials of construction at the bottom of the landfill can be based on the principle of attenuation of groundwater contaminants. The reaction that is simulated is a non-linear equilibrium adsorption of a single dissolved species. However, several different zones with different sorptive and reactive properties are required, e.g., distribution coefficient, decay coefficient, and yield coefficient. It is therefore recommended that further analysis/research on the model equations developed by the author be carried out as to determine the impact of soil bulk density, chemical decay rates and other hydro geological parameters on groundwater contamination. Federal and State Ministries of Environment should consider groundwater protection an issue of paramount importance. Enabling laws should be put in place for waste disposal systems, and these laws should be enforced. A regulatory framework integrating the eight entities identified as shown in Figure 3 should be considered by federal and state governments for the purpose of groundwater management and quality sustainability in the region. This could reduce the adverse effects of the contaminants in this region.
Groundwater Contamination: Performance Limitations and Impacts … 95
REFERENCES Abam, T. S. K. (2016): Engineering Geology of the Niger Delta. Journal of Earth Sciences and Geotechnical Engineering, vol.6, no. 3, 2016, 65-89 ISSN: 1792-9040 (print version), 1792-9660 (online) Science press Ltd, 2016. Abowei, M. F. N. (1989): Mathematical Modelling of Algal Biomass Growth in Nu River. Part 1, Photosynthetic Rate and Optimum Biomass Growth. Journal Nigerian Society of Chemical Engineers (NSChE), vol 8, No 1 p 61. Abraham, M., 1976. Nitrate and Chloride Pollution of Aquifers: A Regional Study with the Aid of a Single-Cell Model. Water Resources Research, 12(4): 731-732. Adepelumi, A. A., Ako, B. D., Ajayi, T. R., Afolabi, O., Omotoso, E. J. (2009): Delineation of Saltwater Intrusion into the Freshwater Aquifer of Lekki Peninsula, Lagos Nigeria. Environmental Geology 56: 927-933. Adesuyi, A. A., Nnodu, V. C., Akinola, M. O., Njoku, K. L. and Jolaoso, A. O.(2015): Groundwater Quality Assessment in Eliozu Community, PH Niger Delta. International Journal of Scientific and Technology Research, volume 4, issue 12, December 2015. Akinwumiju A. S, and Orimoogunje O. O. I. (2013): Predicting the Yields of Deep Wells of the Deltaic Formation, Niger Delta, Nigeria. J Environ Anal Toxicol 3: 168. doi: 10.4172/2161-0525.1000168. Amadi, A. N., Olasehinde, P. I. and Yisa, J. (2010): Characterization of groundwater Chemistry in the coastal Plain-sand aquifer of Owerri using Factor Analysis,’ International Journal of Physical Sciences, vol. 5 pp 1306-1314. Amajor, L. C. (1991): Aquifers in the Benin Formation (Miocene Recent), Eastern Niger Delta, Nigeria, Litho-stratigraphy, Hydraulics and Water Quality’ Environmental Geology and Water Sciences, 17 (2), 85-101. Amangabara, G. T. and Ejenma, E. (2012): ‘Groundwater Quality Assessment of Yenagoa and Environs, Bayelsa State, Nigeria between 2010 and 2011,’ Resources and Environment, vol 2 No 2, pp 20-29. Anderson, M. P. (1979): Using Models to simulate the Movement of Contaminants through Groundwater Flow Systems, CRC Critical Review in Environmental Control, No 9 pp 97-156. Anderson, M. P. and Woessner, W. W. (1992) Applied Groundwater Modeling. Academic Press Inc., San Diego, C. A.; 381 p.
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Ashim, D.G., Poojitha, N.D. and Yapa, D., 1982. Salt Water Encroachment in an Aquifer. Water Resources Research, 18(3): 546-550. Ashim, D. G. (1998): ‘Groundwater and the Environment’. In: Water Resources: Environmental Planning, Management and Development 1998 Ed: Asit K. B. Tata, McGraw Hill, pp 117-203. Asit, K. B. (1998): ‘Water Development and Environment’, In: Water Resources: Environmental Planning, Management and Development 1998 Ed: Asit K. B. Tata, McGraw Hill, pp 8-10. Ayotamuno, M. J. and Kogbara, R. B. (1991): ‘Response of Environmental Characteristics to Industrialization: A case study of the Onne Oil and Gas,’ Journal of Food, Agriculture and Environment, vol 5 No. 1 pp 288289vol 15, No 13 pp 1- 8. Bear, J. and Verruijit, A. (1990): Modeling Groundwater Flow and Pollution; Reidel Dordrecht; Netherlands, p 414. Bouwer, E., Mercer, J. W., Kavanaugh, M. and Digiano, F. (1988): Coping with Groundwater Contamination, Journal of Water Pollution Control Federation, 60 (8), pp 1414-1428. Bredehoeft, J.D. and Pinder, G.F., 1973. Mass Transport in Flowing Groundwater. Water Resources Research, 9(1): 194-210. Calow, R. C., Robins, N. S., Macdonald, A. M., Macdonald, D.M. J., Gibbs, B. R. (1997): ‘Groundwater Management in Drought-prone Areas of Africa’. International Journal of Water Resource Development 13: 241261. Carter, R. C. (1988): The development of small-scale irrigation in sub-Saharan Africa. Public Administration and Development 9: 543-555. Edet, A. E. (2004): ‘A Preliminary Assessment of rare earth elements concentrations in an acidic fresh groundwater (South Eastern Nigeria),’ Applied Earth Sciences, Trans. Inst. Min. Metall. B) vol 113, pp 100-109. EPA Hand Book (1994): Groundwater and Wellhead Protection, Sept 1994 pp 1-10. Fatta, D., Naoun, C., Karlis, P. and Loizidou, M., 2000. Numerical simulation of flow and contaminant migration at a municipal landfill. Journal of Environmental Hydrology, 16(8): 1-11. Freeze, R. A and Cherry, J. A. (1979): Groundwater. Prentice-Hall Publishing Co., Englewood Cliffs, N. J p 604. Garg, S. K. (1998): Water Supply Engineering. Environmental Engineering, Khanna Publishers 1: 112. Inyang, I.T. (2004): Assessment of Water Wells in Ekpiri Nsukara. Upbl B. Eng Project Department of Civil Engineering University of Uyo, Nigeria.
Groundwater Contamination: Performance Limitations and Impacts … 97 Konikow, L. P. (1981): Role of Numerical Simulation in analysis of Groundwater Quality Problems. In: Proceedings International Symposium on quality of Groundwater, Noordwij Kerhout, Netherlands. Mercer, J.W., Lyle, R.S. and Charles, R.F., 1983. Modeling Ground-Water Flow at Love Canal, New York. Journal of Environmental Engineering, 109(4): 924-941. Mutsa, M., and Mark, F. G. (2007): Sub-Saharan Africa: Opportunistic Exploitation. CAB. NDES Report (1998): Niger Delta Environmental Survey Report, Phase 2 Report. Hydrology and Hydrodynamics. Vol 1. Hydrological Characteristics and Resources. NRC, 1994. National Research Council, Alternatives for Groundwater Clean Up. National Academy Press, 336 pp. Nwachukwu, D. O. (2001): Hydrogeological Report of Dredging Activities on Amadi Creek, PH. Ophori, D. U., Gorring, M, Olsen, K., Orhua, E. and Hope, J. (2007):’A preliminary analysis of groundwater chemistry in shallow boreholes, Ughelli, Nigeria’ Journal of Environmental Hydrology, vol. 15, No. 13, pp 1-8. Oteri, U. A. (1981): A Study of the Effects of Oil Spills on Groundwater. In: Proceedings of 1981 International Seminar. The Petroleum Industry and the Nigerian Environment, p 89. Oteri AU (1984) Electrical Log for Groundwater Exploitation in the Niger Delta. In: The Challenges in African Hydrology and Water Resources. IAHS, UK. Oteri A. U. and Atolagbe F. P. (2003) Saltwater Intrusion into Coastal Aquifers in Nigeria. ICSICA. Mexico. Omosuyi GO (2008) Geoelectric Sounding to Delineate Shallow Aquifers in the Coastal Plain Sands of Okitipupa Area, South-western Nigeria. PJST 9: 562-577. Park, J., Bethke, C.M., Torgersen, T. and Johnson, T.M., 2002. Transport modeling applied to the interpretation of groundwater 36 Cl age. Water Resour. Res., 38(5): 1043. Rahman, M.M. and Shahid, S., 2004. Modeling Groundwater Flow for the Delineation of Wellhead Protection Area around a Water-well at Nachole of Bangladesh. Journal of Spatial Hydrology, 4(1). Sauty, J. P. (1980): An Analysis of Hydro Dispersive Transfer in Aquifers. Water Resources Research, vol 16, No 1, pp 145-158.
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Schwartz, W.F., Cherry, A.J. and Roberts, R.J., 1982. A case study of a chemical spill; Polychlorinated Biphenyls (PCBs) in hydrogeological conditions and contaminant migrations. Water Resources Research, 18(3): 535-545. Short, K.C and Stauble, A.J (1967). Outline geology of the Niger Delta. Bull. Am. Ass. Petrol Geol. 54:761 – 779. Spanoudaki, K. et al., 2005. Integrated Surface Water-Groundwater Modeling. Global Nest Journal, 7(3): 281-295. Stefan, H. and Hermann, K. (Editors), (2003). Geometric Analysis and Non Linear Partial Differential Equation. Springer-Verlag Berlin Heidelberg New York. Teme, S. C. (2002): ‘Impact of Environment on land, air and water’ Inaugural Lecture delivered at Rivers State University of Science and Technology, Port Harcourt, Nigeria. Ujile, A. A. (2003): Modeling Groundwater Contaminants due to Transient Sources of Pollutants. PhD Dissertation. RSUST, Nigeria. Ujile, A. A. (2007): Modeling Leachate Transport in a Sanitary Landfill SystemNiger Delta as a case Study. Journal of Solid Waste Technology and Management. Chester, PA19013-5792 USA. (33) 4 183-192. Ujile, A. A., Abowei, M F N. and Amadi, S. A. (2008): 'Groundwater Contamination Processes in Coastal Towns in Niger Delta- Nigeria. In 1st Post Graduate Researchers' Conference 2008, University of Abertay, Dundee, Scotland, United Kingdom, 29- 30 September, 2008. Ujile, A. A., Omo-Irabor, O. O. and Joel, O.F (2012): Groundwater Contamination at Waste Disposal sites at Ibadan, Nigeria, Journal of Solid Waste Technology and Management. (38)3,149-156 www.solidwaste.org/journal/abstracts. Ujile, A.A. (2001): Modeling iron, chloride, salinity as groundwater contaminants in parts of Niger Delta. Nigerian Society of Engineers (NSE) Technical Transaction. April- June (2)36 67-72. Ukpong, E.C. (2011): Groundwater Quality at Idu Uruan Water Headwork and Adjoining Environment in Akwa Ibom State, Nigeria. Journal of Environmental Issues and Agriculture in Developing Countries. Vol.3 No.3 pp 106-112. USEPA (1996): United States Environmental Protection Agency. Guide to Pollution Prevention Series. USEPA (2002): Guide Internet url: http//
[email protected]/safe.water.
Groundwater Contamination: Performance Limitations and Impacts … 99
APPENDIX A Concentration Profile of Iron contaminant in groundwater in Yenagoa MATHCAD input data for Yenagoa, Nigeria h 500 m Dx
2 2 m 2.1 10 s
Dy
8.6 10
Vx Vy
m2
3
8.810
6
s m
1.9 10
7
s m s
b
1.9
g L
0.5355 mg Co 4.5 L L Kd 2.6 g Kd R 1 b
R 10.225
1
A( a)
Dx 2 h
Vx
B( b)
Dy 2 h
Vy
P( a)
Dx 2 a Vx 1 ( a 1) h
Q( b)
Dy 2 h
a ( a
1)
1 b ( b 1)
b Vy
1 (b
1)
Mathcad program for = 0.5355
M( a b)
t
2 yr
Dx 2 h a
Dy 2 h b
a) Vx
(1 a
b Vy
1 b
Awajiogak A. Ujile
100
7 t 6.311 10
s
K KLR 7 1 K 3.17 10 s M( ab ) ( ab ) K KL
3.1 10
8
1
s
h
( ab) t R
Co ( a b ) e
C( a b )
( ab ) t R
e C( a b) h
CI( a b) A( a)
B( b)
P( a)
alow 0.1 ahigh 1 an 6 i 0an 1 ahigh aind i
alow
i
an
alow 1
blow 0.009 bhigh 0.099 bn 6 j 0bn 1
bind j C
i j
CIi j
blow
bhigh blow j bn 1
C aindi bindj CI aindi bindj
1 Q( b )
Groundwater Contamination: Performance Limitations and Impacts … 101
APPENDIX B Mathcad output for C and C1 for Yenagoa 4.24910 3.81310 3.71910
C
3.67710 3.65410 3.63910
8 8
1.533 10
8
1.438 10
8
1.397 10
8
1.374 10
8
4.656 10 4.675 10 CI
1.968 10
4.679 10 4.682 10 4.683 10 4.684 10
1.359 10 3 3 3 3 3 3
8
1.51210
8
1.07710
8
9.82110
8
9.40710
8
9.17510
8
4.852 10 4.962 10 4.995 10 5.012 10 5.021 10 5.028 10
9.02610 3
8 8
5.328 10
3
7.22 10
9
5.304 10
3
7.452 10
9
5.265 10
3
7.866 10
9
5.187 10
3
8.812 10
9
4.969 10
3
1.316 10
5.345 10
3 3 3 3 3
9
6.36710 6.13510
9
5.369 10 5.497 10 5.565 10 5.608 10 5.637 10
5.98710 3 3 3 3 3 3
7.035 10
9
6.78 10
9
1.139 10
9
7.72610
9
5.047 10
8
1.20810
9
7.072 10 3
8
6.09 10
9
5.446 10
9
5.298 10
5.103 10 5.519 10
3 3
3
5.7 10
5.865 10 5.91 10
kg m
9
3
s
1
9
5.145 10 5.645 10
6.013 10 3
3
9
5.878 10
3
5.8 10
9
9
5.677 10
9
8
6.102 10 6.164 10
3 3 3
kg m
3
3 3 3
Appendix B1. Bar Plots for C and C1 from Matrices Solution of Appendix B
0.00 6 4 10 3 10 2 10
1 10
8 8
0.00 4
8 8
0.00 2
0
0 1
C
2 3 4 5
5
4
3
2
1
0 00
CI
1
2
3
4
5
1 0 54 32
Awajiogak A. Ujile
102
Appendix B2. Surface Plots for C and C1 from Matrices Solution of Appendix B
4 10 3 10 2 10
1 10
8
0.00 6
8 0.00 55
8 8
0.00 5
0
1
0 1 2 3 4 5
2
3
4
0
5
1
2
3
4
0 1 2 3 4 5
C
5
CI
Appendix B3. Contour Plots for C and C1 from Matrices Solution of Appendix B 1
1 0.00 5 0.00 6
0.5
0.5
0
0
1 10
8 1 10
0.5
0.00 6
0.00 5
0.00 6
8 1.5 10
0.00 6
0.00 6 0.00 5 0.00 5
0.00 5
0.5
0.00 6
0.00 6
0.00 5
1
0.00 5 0.00 5
0.00 5 0.00 5
0.00 5 0.00 5
0.00 5 0.00 5
1 1
C
0.00 5
8
8 1.5 10
0.00 5
0.00 6
0.5
0
0.5
1
1
CI
0.5
0
0.5
1
