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In this research work, the effect of environmental pollution on the dissolved oxygen resources of a receiving stream, Amadi creek, was investigated .Amadi creek, located in Port- Harcourt metropolis is a unique creek that is of high economic importance to the residents of Rumuobiakani, Mini-Ewa, Oginigba, Woji and Okujagu communities as it hosts the activities of the majority of the companies around the Trans- Amadi Industrial area and also provides water for fishing and water transportation The study was carried out to evaluate the water quality changes resulting from increasing human and industrial activities in and around the creek. For this purpose the physic o -chemical characteristics of the water in the creek at different seasons were measured and the results compared against W.H.O standards. Statistical methods were used at some point to calculate the mean, variance and the standard deviations in all stations and the results were then presented using computer based excel spreadsheet. The results show that the creek has relatively low concentrations of heavy metals ranging from (0.26-0.30mgl), (0.00-0.01mgl), (0.01-0.02mgl), and (0.85-1.17mgl for chromium, copper, aluminum and iron respectively. Mean values of other physic o- chemical parameters like temperature, salinity, suspended solids, pH, DO, BOD, range from (22.1-29.5oC), (0.1-2.7mgl), (7.0-59.5mgl), (6.3-8.4), (2.3-5.11mg)],(0.8-5.7mgl) respectively. Dissolved oxygen water quality standards for creeks and rivers require the maintenance of DO level of 5mgl or more at any time. However, practical analysis of the water samples for dry and wet seasons showed that the conditions in the creek fall below this standard. .Measured DO concentrations were found to be as low as 2.3mgl. Hence this research attempted to solve this problem of DO depletion by optimizing the locations of waste discharge locations into the creek. The DO deficit equations are solved by the methods of simple calculus (classical optimization), which simplifies the mathematical solution of the model equations by avoiding difficult to evaluate integrals. Two scenarios were identified and used to investigate the effect of BOD on the DO level in the stream, using mathematical simulation techniques. Simulation results of the two scenarios suggest that the dissolved oxygen deficit is dependent on the distance between waste discharge points .Hence to ensure minimum impact on water quality, waste discharge locations should be placed at the optimal locations of 10015m and 6992m upstream and downstream waste discharge points respectively, at an optimum DO deficit of 4.14 mg/l for the first scenario, and at 41233m, 40995m, 33605m upstream and downstream waste discharge points respectively for the second scenario at an optimum DO deficit of 4.57mg/l. This means that if a new waste input ( e.g., a new sewage treatment plant) is proposed for a stream or river, both its BOD input and the proposed location with respect to the other inputs are important in order to determine the effects of pollution on the stream DO level. Comparing the Dt values predicted by the new models with Ugbebor, the new models are in good agreement with the values of observed Dt with a standard error of 1.05%. It is recommended that Industrial establishments planning to site their treatment facilities along rivers or streams should be compelled to discharge their waste stream in compliance with the optimal locations (with respect to any existing plant) ,and the existing effluent standards, so as to avoid undue dissolved oxygen (DO ) depletion .
Key words: waste discharge point, pollution, optimal locations, waste water, simulation
TABLE OF CONTENTS
Title page i
Approval page iv
Table of Contents viii
List of Figures xii
List of Tables xiv
1.0 Introduction 1
1.1 Background 4
1.2 Work Justification 9
1.3 Definition of the Problem 10
1.4 Research Objectives 11
1.5 Scope of Research 11
1.6 Significance of research 12
- Literature Review 13
- Sources of Pollution in Rivers 12
- Effect of Pollution in Aquatic Environment 19
- Assimilatory Capacity of Stream 22
- Factor Affecting Self-Purification of Streams 25
2.4.1 Hydrodynamic Factors 27
2.4.2 Environmental Factors 27
2.4.3 Climate Factors 27
2.5 Water Quality 28
2.5.1 Water Quality Assessment 30
2.5.2 Assessment Approaches 31
2.5.3 Assessment Operations 32
2.6 Effect of Point and Non-Point Discharge on Water Quality 32
2.7 Water Quality Models 35
2.7.1 Re aeration 38
2.7.2 Transport 49
2.7.3 Empirical Models 51
2.7.4 Deterministic Models 58
2.7.5 Stochastic Models 62
- Site Description 64
- Sources of Data 67
- Parameters of Interest 67
3.3.1 Biochemical Oxygen Demand (BOD) 68
3.3.2 Dissolved Oxygen (DO) 69
3.3.3 Temperature 69
3.3.4 pH 70
3.3.5 Heavy Metals 71
- Experimental Set-up 71
- Sampling Locations 72
- Method of Sampling 73
- Laboratory Analyses of Samples 73
3.7.1 Temperature Analysis 74
3.7.2 pH analysis 74
3.7.3 Biochemical Oxygen Demand Analysis 75
3.7.4 Dissolved Oxygen Analysis 76
3.7.5 Metal Analysis 78
3.8 Statistical Analysis 80
- Mechanism of Pollution Fate in the Environment 82
- Derivation of the deficit equation 82
- Formulation of Equations for Multiple Waste Discharge
Location into Rivers 83
- Case 1 – One Source of Waste Water Discharge 83
- Case 2- Two Sources of Waste Water Discharge 89
4.3 Mathematical Model 97
RESULTS AND DISCUSSION
5.1 Sensitivity Analysis 112
5.1.2 Effect of Velocity on the Optimal DO deficit 112
5.1.3 Effect of ultimate BOD on Optimum DO deficit 114
5.1.4 Effect of initial DO deficit on optimum DO deficit 114
5.1.5 Variation of optimum DO (Lo) deficit with distance 116
5.1.6 Effect of ultimate BOD (Lo) on Optimal Locations 117
5.1.7 Effect of Initial DO deficit on Optimal Location 120
5.1.8 Effect of velocity on Optimal Locations 122
5.2 Case studies 125
5.2.1 Effect of Flow conditions on Single Point Source Discharge 126
5.2.2 Effect of Flow Conditions on Two Sequential Point Source Discharge 127
CONCLUSION AND RECOMMENDATION
Contribution of Knowledge 134
Pollution is the befouling of the environment by the disposal of solid, gaseous, and liquid waste products resulting from human activities (Agunwamba, 2001).
Agunwamba(2001) further submits that pollution of the marine environment is the introduction by man directly or indirectly of pollutants which result in such deleterious effect as:
- Harm to living organisms
- Hazards to public health
- Hindrance to marine activities (e.g., fishing)
- Impairment of water quality with respect to use, and
- Reduction of amenities.
The deterioration of water quality in rivers, estuaries and coastal regions has been an alarming outcome of ever increasing discharge of industrial and municipal wastes. Wastes are discharged at selected points along rivers or oceans which create local high levels of pollution. However, the natural mixing and dispersion processes facilitate the reduction of the local pollution level by distributing the dissolved substances gradually over time. Dispersion is the action by which water flowing in a river or ocean water body spreads out and dilutes a mass of pollutant .Rather than moving downstream as a slug, such a mass is distributed along the length of the river, some parts moving faster and some slower than the mean flow velocity. The distribution of the average cross-sectional concentration is highly skewed at first, characterized by high concentration values within a short zone and a tapering tail in the upstream direction. The distribution becomes Gaussian after some large flow time (Fischer,1968;Smith,1986).The Federal Environmental Protection Agency FEPA (1991) defined pollution as “Generally the presence of matter of energy whose nature, location or quantity produces undesired environmental effect”. Under the Clean Water Act, for example, pollution is defined as the man-made or man-induced alteration of the physical, biological and radiological integrity of water. Water pollution therefore is concerned with the effect of contaminated water on the environment. Contaminated waste is treated to ensure the end products of treated processes are compatible with existing environmental resources and not overtake the assimilatory powers of the water body (Howard et al, 1985). Improperly treated or untreated liquid waste from industries, shops, and residencies discharged into receiving water bodies will lead to pollution on vegetation existing fauna/flora, etc (Bowman et al, 1974), as untreated waste water can enter soil, and mix with rivers and streams causing upset to creatures within the ecosystem. When untreated and treated domestic and industrial waste is discharged into natural bodies of water, the situation becomes even more complex. The discharge of domestic and municipal waste water, industrial and agricultural waste (organic, inorganic pollutants and heat), solid and semi-solid refuse to the streams and creeks result in the accumulation of sediments in watersheds. This reduces the rate of self -purification due to the depletion of dissolved oxygen level in the water, which in turn initiates the anaerobic conditions at watersheds. Therefore, precautions should be taken to restrict the discharge of such wastes into creeks, rivers and other marine environments. The quality of municipal, industrial and agricultural wastes should be controlled at the point of generation. This means the water should be treated before being discharged into any marine environment. The human waste, drinking water and communicable diseases are directly related. Water contamination is measured by the level of pollutants present in a sample. All successful Rivers Basin Management must be based on data obtained for that creek or river in question (Brown et al,1971).This information includes the knowledge of water quality profiles, criteria, impacts and control strategies upon which value judgments can be made. Criteria here refers to the scientific requirements upon which decisions are based on concerning the suitability of the water quality to support a designated use(Gordon et al,1971), while standard refers to legally statutory authority like the World Health Organization (WHO) and the Federal Ministry of Environment ( formerly known as the Federal Environmental Protection Agency .FEPA),based on scientific parameters .It is therefore in the interest of the populace to restore and maintain the chemical, physical and biological integrity of natural water and in addition to making the water safe to drink to provide for the projection and propagation of fish, shell fish etc and provide for recreation on water (Davis et al, 1988). Most of the towns and villages in the Niger delta area of Nigeria have suffered severely from water pollution resulting from oil spillages and effluents discharged into water bodies according to Atorudibo (2007). The Amadi creek is a typical example of a water body in the Niger delta region of Nigeria that has been highly polluted. Almost all industries in Nigeria, continues Atorudibo (2007) generate wastes which in most cases are disposed off without due regard to sound environmental management practices. These industries include petroleum and petrochemicals, steel, plastics, paints chemicals, fertilizers, battery and textile. Industrial activities have gradually led to the degradation and contamination of these water bodies. The pollution of the urban environment, according to Udosen et al (1987) as cited in Atorudibo (2007), are as a result of man’s determination to match his desire with production, through the establishment of various industries which have high potentials to pollute the environment. Many authors, he submits have reported that the Nigerian Environment has deteriorated tremendously (Oluwande,1974; Pickford,1981),and mostly affected is the Niger delta environment (Odu,1981). Amadi creek, the study area suffers a great deal in this respect, hence the need for the physiochemical evaluation of the creek, and the data obtained will be used to, amongst other things, assess the potential impact on human and aquatic life of the environment.
Marine disposal of liquid waste presents a very safe, effective and economical option of waste disposal. For coastal communities, disposal of partially treated waste water through a marine outfall should be considered as an alternative to conventional processing (Viessman and Hammer, 1985).
The ocean disposal of liquid waste is an old practice (Obika et al.,1988). However, according to (Pergamon press.1959,1975; Hansen, 1977; Fernando,1977; Hill and Mobb,1985; IAEA,1984),as cited in Obika et al., (1988), its impact on marine water quality and its related effects on man and the marine environment have only recently been of serious concern
For safe dumping of wastes, submits Obika et al.,(1988), its dispersal from the dumping site and its after-effects need to be predetermined and re-assessed. In the process of the assessment of marine waste dumps, concentrations of pollutants at various distances from the site are estimated utilizing mathematical simulation techniques of the dispersion of wastes in the ocean water body. Extensive studies have been performed in the area of waste dispersion and decay in fresh waters, in inland rivers and lakes, according to (Hill,1977; ;James,1984),as cited in Obika et al.,(1988). However, direct application of such models to seawater is not feasible due to physical, chemical, and biological differences between the two systems. Several studies ,according to (Alexander,1975; Grace,1978; Arceivala,1978; Garret,1987),as cited in Obika et al.,(1988), have also reported on the dispersal of pollutants from municipal and industrial wastes and their decay in the sea water. Dispersion and decay are affected by convection and mixing processes such as vertical mixing due to buoyant forces that result from differences in densities of waste and sea water, waste discharge velocity and jet size, wave actions on vertical and horizontal mixing, eddy mixing, ocean bottom deposition, ocean bottom biological and chemical activities and decay of pollutants caused by biological and chemical processes sustained in the water body and bottom deposits.
The process of waste spread and decay into the water surrounding waste dump sites, according to (McBride,1973; Arceivala,1981; Garret,1987),as cited in Obika et al.,(1988) have been modeled starting from complicated ones that include all relevant factors to very simplified ones that focus on unidirectional hydraulic flow with average dispersion and decay coefficients. For control of marine environmental pollution the utility of such models is immense. These models can be utilized for single or multiple waste discharge points with preset locations along the coast line.
Creeks and rivers are used as open channels for the discharge of waste water. Of recent, many creeks and rivers have been greatly polluted with municipal and industrial activities causing an imbalance in the natural environment .With increasing demands on water resources and contamination from industrial waste and human activities, the potential outbreaks of water-borne diseases in creeks and rivers dwelling areas continue to increase. The physico-chemical properties of rivers and creeks could be affected by internal and external factors. Meteorological events and pollution are a few of the external factors that affect physico -chemical parameters such as temperature, pH, salinity, hardness, dissolved oxygen and phosphates of the water. These parameters have major influences on biochemical reactions that occur within the water body. Sudden changes of these parameters may be indicative of changing conditions in the water body. Internal factors, on the other hand, include events, which occur between and within bacteria and plankton populations in the water body (Nubel et al,1999) .There is an intricate relationship between external and internal factors in an aquatic environment The effects of environmental pollution on creeks and rivers especially in the Niger delta, has been of paramount concern due to the ever increasing industrial activities, principally oil exploration, carried out in them. This has challenged many researchers to seek for solution to these environmental challenges. Sometimes wastes are discharged into creeks and rivers arbitrarily without predetermining the impact of such discharges on aquatic life (Agunwamba et al, 2006). Oil producing and petroleum refining companies are among the biggest polluters in the Niger delta environment where more than 2000 barrels of crude oil are spilled annually into the water bodies according to Atorudibo( 2007). The rivers and streams in the Niger delta are now becoming increasingly vulnerable to human and industrial activities operating in and around them reports Agbozu et al(2004) as cited in Atorudibo (2007). Ogan (1998), as cited in Agbozu et al(2004), observed that wastes both untreated and inadequately treated are discharged into river systems in the Niger delta. Such discharges according to Agbozu et al(2004) are made directly or via open channels. The rivers, continues Agbozu et al(2004) flow through a number of communities, providing drinking and recreational water for large populations of the communities. It may be interesting to note submits Ikpe (1999) as cited in Atorudibo (2007), that in recent times there has been a tremendous increase in human and industrial activities in these coastal areas, including oil exploration activities. These activities impact negatively on the rivers and creeks, thereby degrading their water quality. Also Princewill (1988) submits as cited in Agbozu et al (2004) that virtually all the aqueous wastes from industries in Port-Harcourt and its environs are discharged into streams and creeks which drain into the Bonny River system, endangering its quality. In an independent survey, Ekweozor (1985) concluded that the Bonny River system is under serious stress resulting from the loadings of industrial discharges by industries sited along the rivers and creeks as is the case in the study area. The discharge of municipal waste water and industrial waste water containing organic impurities poses a serious environmental problem. This is because the decomposition of this organic material by bacteria results in the utilization of dissolved oxygen. The replacement of the oxygen by re aeration occurs through the water surfaces exposed to the atmosphere reports Agunwamba et al (2006). Much research have been done on the area of water pollution especially regarding the mechanism of re-aeration, assessment of assimilatory capacity of streams, models of re-aeration according to (Mcbride, 1982; Dobins,1964; Cohen, and O’Connel 1976; Campolo et al 2007), as cited in Agunwamba et al (2006). However, not much research have been done on the area of optimizing the location of waste discharge points to improve water quality through possible legislation as is the case with this study. Such a study was conducted in Amadi creek, Port Harcourt, Rivers State Nigeria. Amadi Creek is an important resource which sustains fishing activities and also provides a medium for waste water disposal both by the communities around the Trans-Amadi Industrial area near the creek. Although the self purification process which occur in a stream enable it to safely handle some waste water discharges, there is a limit to its assimilatory capacity. Not recognizing that the creek has a limited capacity some companies and communities discharge waste waters haphazardly into the creek thereby jeopardizing the health of aquatic life. There is therefore the need for proper assessment of the creek to ensure control of waste water discharges within the creek’s assimilatory capacity which will subsequently result in improved water quality and optimum utilization according to Robert (1995) as cited in Agunwamba et al (2006). Hence, this study seeks to solve this problem by optimizing the location of waste water discharge points into the creek.
- Work Justification
Some of the motivational reasons for embarking on this research include; but not limited to the following:
The environmental and safety impact of liquid waste disposal in common with many developing countries. Nigeria is currently facing a serious and worsening waste water treatment and disposal problem. Several reasons are responsible for this, three most important being, high annual growth of population, rapid progress of industrialization and urbanization, and inadequate capital and technological resources. Nigeria has experienced an unprecedented growth in population which resulted in ever increasing rate of water demand and the attendant requirement for improved water quality. The greatest threat to improved water quality is discharge of untreated sewage into fresh water bodies. While it is estimated that the water requirement for agricultural, domestic and industrial uses are likely to double by the next decade, our fresh water bodies are becoming more and more unfit for use due to discharge of untreated sewage and industrial effluent into them .Secondly, the Amadi creek serves as waste dump sites for the companies operating around it, and as toilet for the communities through which they pass due to the high cost of constructing a modern toilet facility. This singular fact encourages eutrophication of water hyacinth thereby inhibiting fishing activities. Based on the above facts and waste discharges at various points along the creek makes it imperative to adopt methods which are geared towards protecting the creek from pollution. Therefore, information regarding the physico-chemical parameters of the creek must be provided at all times, hence the need for this study.More importantly, the findings will reveal the extent of environmental pollution from the communities and the industrial activities along the creek on water quality will serve as a baseline data for effective management and monitoring, for future purposes.
- Definition of the Problem
Amadi creek traverses the Trans -Amadi Industrial area of Port Harcourt metropolis. Major activities in and around the creek include butchery, trading, fishing, bathing and washing of clothes and utensils. Various communities located around the creek use it for domestic and commercial purpose. Not recognizing that the creek has a limited capacity for self purification some companies and communities discharge untreated waste water haphazardly into the creek, thereby jeopardizing the creek’s ecosystem and other beneficial uses .Due to the importance of this creek to the host communities, and the increased and continuous use of this creek, the water quality has been affected tremendously posing a serious threat on the people’s livelihood and aquatic life. It then became imperative to assess the water quality of the creek to ensure control of waste water discharges within the stream’s assimilatory capacity and relate the data obtained to current international water quality standards.
- Research Objectives
The main objective of this research is to determine the optimum discharge points for minimum effects of pollutants in rivers:
The specific objectives are:
- Determine the geometrical and hydrodynamic characteristics of the river
- Measure the flow rates and the concentrations of pollutants from different point sources, including the BOD, DO, temperature and pH at various intervals of distance along the river
- Determine pollutant dispersion characteristics of the river
- Formulate and solve the equations for multiple waste discharge locations into rivers.
- Calibrate and verify the equations using experimental and field data
- Optimize multiple waste discharge points for minimum impacts on water quality.
- Scope of Research
The research will be limited to the hydrodynamics of pollutant transport and physico -chemical analysis of the quality of one river. On account of time constraint, only one year data was used.
- Significance of Research
The implementation of this work will offer the following benefits:
- Minimization of waste disposal cost in the marine environment
- Control of marine environmental pollution
- Enhancement of water quality
- Promotion of marine activities (e.g fishing)
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