ABSTRACT 
This report presents results obtained from the investigation and water sampling exercise carried out on the segment of River Illo that passes through Sango in Ado Odo-Ota Local Government Area, Ogun State, Nigeria. The report reveals that while some people used water from the river for domestic, food production and recreation purposes, others discharge their wastes without any form of pre-treatment into it. The multipurpose usage of water from River Illo by local residents thus hinges public health on the self purification capacity of the river alone.    
Information on water use and waste disposal practices of the local residents were obtained through direct observation and oral interview of members of randomly chosen households built along the river within a distance of 2km. Single grab samples of water were obtained from the river at the site of an abattoir effluent discharge at distances 0m, 10m, 20m, 30m, 50m and 100m from the point of discharge. A seventh sample was also obtained 10m upstream of the point of effluent discharge to furnish information on ambient conditions of the river prior to pollution while an eighth sample which was prepared by diluting the water obtained at 0m with distilled water (i.e. 25%  stream water, 75% distilled water) was included to serve as control sample. All water samples were transported (within 3 hours of isolating them from the river body) to the laboratory for analysis and the results were subjected to graphical, statistical and mathematical analysis. Pollution from the abattoir caused a drop in dissolved oxygen level of the river from an ambient value of 4.6mg/l to 0.01mg/l at the point of discharge. The pollution also caused an increase of 447.5mg/l to 1071.5mg/l in T.S., 0.04mg/l to 4.4mg/l in ammonia, 170mg/l to 670mg/l in BOD, 0.05mg/l to 3.05mg/l in phosphorus, 50mg/l to 1066.7mg/l in alkalinity and 18mg/l to 820mg/l in Acidity. It was also found out that between 30m " 80m downstream of the pollution point, a threat of eutrophication is caused by plants growing in the river path. Despite this obstruction, the river recovered considerably to a D.O. level of 3.9mg/l at 100m downstream. Results from the dispersion modeling shows the self-purification capacity of the river, f, to be 1.1 within 30m distance from the point of discharge and 0.8 between 30m and 100m from the point of discharge. The results from the application of the Streeter-Phelps model showed that the eutrophication occurring between 30m " 80m is interfering adversely 
with the self purification processes of the river.   The percentage compliance of each of the eight water samples with Guideline Values (GLV) of WHO and FEPA was performed. None of the samples met the minimum requirements for BOD, COD and TSS, which are indicators of pollution. It was concluded that River Illo is being polluted by abattoir effluents discharge thereby exposing the health of local residents who use the water from the river for domestic, recreation and food production purposes to avoidable risks. Suggested actions that could further complement the self-purification capacity of the river were offered.

TABLE OF CONTENTS
CHAPTER ONE: INTRODUCTION
1.1 Background information
1.2 General Description of River Illo
1.2.1 Identified Sources of pollution
1.2.2 Water Uses and Conflict
1.3 Statement of the problem
1.4 Justification of the Study
1.5 Objectives of the Study
1.6 Expected Contributions to Knowledge
1.7 Scope of the Study
CHAPTER TWO: LITERATURE REVIEW
2.1 Surface Water Quality and Anthropogenic Activities
2.2 Slaughterhouses
2.2.1 Characterization of slaughterhouse wastes
2.2.2 The Nigerian Experience
2.2.3 Abattoir Waste Management
2.2.3.1 Waste Treatment Methods
2.2.3.2 Pollution Prevention
2.3 Parameters Frequently Examined in the Determination of Water Quality
2.3.1 Physico-ChemicaParameters
2.3.2 Microbiological Parameters
2.4 Water Pollution and Control in Nigeria
2.5 Water Laws and Standards
2.6 Water Quality Measurements and Quantitative Hydrology
2.6.1 Assimilative Capacity Studies
2.7 Field Survey and Sampling
2.8 Quality Control and Assurance
2.9 Data Interpretation
CHAPTER THREE: METHODOLOGY
3.1 Field Survey and Sampling Exercise
3.2 Sampling Locations
3.3 Conditions of Sampling
3.4 Quality Control and Assurance
3.5 Laboratory Analysis
3.6 Data Analysis
3.7 Solid Waste Management
CHAPTER FOUR: RESULTS AND DISCUSSIONS
4.1 The Abattoir
4.2 Solid Waste Characterization and Management practice at the abattoir
4.3 Hydraulic Data
4.4 Water Quality Parameters
4.4.1 Physical Parameters
4.4.2 Chemical Parameters
4.4.3 Microbiological Parameters
4.5 Correlation and Regression Analysis
4.6 Percentage Compliance with Standards
4.7 Descriptive Statistics
4.8 Self purification capacity of stream
4.9 Dispersion Modeling
4.9.1    Determination of Coefficient of Dispersion
4.9.2    Dissolved Oxygen modeling
4.9.3    Assumptions of the model
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION
5.1 Conclusion
5.2 Recommendation
REFERENCES
APPENDIX
LIST OF TABLE
2.1    Physico-Chemical Parameters of Water Quality Importance
2.2    Nigerian States, key Industries and Waste Characterization
2.3    Water Quality Parameters and Storage Conditions for Samples
3.1    Hydraulic properties of the sampling points
4.1    Hydraulic Data from the River
4.2    Physical Parameters of the Water Samples from River Illo
4.3    Chemical Parameters of the Water Samples from the River
4.4    Microbiological Parameters for the river
4.5    WHO Guideline Values and Percentage Compliance of samples
4.6    Descriptive Statistics
4.7    Self purification factor for receiving water at 200C
LIST OF FIGURES
1.1    Map of Ota District Showing Important Settlements and Rivers…
3.1    River cross section and Dimensions obtained
3.2    Distances along the river where samples and hydraulic   
    measurements were obtained
3.3    Sketch of the site plan of the abattoir and sampling   
    points along the river
4.1    Graph of discharge against velocity
4.2    Graph of conductivity against Total Solids
4.3    Graph of discharge against conductivity
4.4    Graph of Velocity against Dissolved Oxygen
4.5    Graph of Velocity against Phosphate
4.6    Graph of Ammonia against Alkalinity
4.7    Plot of Total Solids against the Sampling Points
4.8    Plot of phosphate against the Sampling Points
4.9    Plot of COD against the Sampling Points
4.10    Plot of Ammonia against the Sampling Points
4.11    Plot of Dissolved Oxygen against the Sampling Points
4.12    Ideal Dissolved Oxygen Curve
4.13    Dissolved Oxygen Curve for Case Study
LIST OF PLATES
1.    Dug well supplying process water
2.    The Slaughtering Slab
3.    A section of the receiving river
4.    Accumulated sludge in contact with the water body
5.    Animal bones being sun dried
6.    Land and water pollution from rendering activities
ABBREVIATIONS AND SYMBOLS
ACS – Assimilative Capacity Studies
ASP – Activated Sludge Pond
BOD – Biochemical Oxygen Demand
COD – Chemical Oxygen Demand
D.A.F. – Dissolved Air Floatation
D.O. – Dissolved Oxygen
E.C. – European Communities
F.E.P.A. – Federal Environmental Protection Agency G.E.M. – Global Environmental Monitoring Systems mg/l – milligram per liter
NPC – National Population Commission
POC – Pollutants of Concern
TDS – Total Dissolved Solids
TSS – Total Suspended Solids
TS – Total Solids
µs/cm – microsiemen per centimeter
WHO – World Health Organization
-DL = m2/s, where the negative sign is to show the flow of molecules from area of higher concentration to lower concentration
Da = initial DO deficit
La = initial BOD
q = kg/m2s, where q is flux
Cs = concentration of D.O. at saturation
C1 = mg/l, where subscript 1 stands for point 1
r d  = mg/m3d, is the rate of deoxygenation
Di, ti = dissolved oxygen, time, at point of inflexion
Dc, tc = dissolved oxygen, time, at critical point
Xc, Xi = distance at which Dc, Di occurs
K1,1 = deoxygenation rate in segment 1
 CHAPTER 1
INTRODUCTION
1.1 Background Information
Water constitutes seventy percent of the total earth surface. Of all this, 97.5% is salt water and of the remaining 2.5% fresh water, 70% is frozen in the polar ice caps. The other 30% is mostly present as soil moisture or is trapped in underground aquifers. In the end, less than 1% of the world’s freshwater (or about 0.007% of all water on earth) is readily accessible for direct human use (Peace corps, 2006) Surface water is the most readily available, yet the most polluted as a result of anthropogenic, but happily, controllable activities. Surface water is found mainly in the hinterlands. In developing countries, especially the rural areas where potable water supply is a near rarity, most of the dwellers rely solely on surface water in streams, brooks, rivers, ponds and lakes. Unfortunately, most of our rural dwellers do not appreciate the enormity of the risk attached to unhygienic water use.
In Nigeria for instance, the 1991 census made it clear that only 37.7% of our entire population lived in urban areas while the remainder lived in rural areas (NPC, 2005). It was also revealed that growth rate was 2.9%. This shows that today, an estimated 85 million out of 136.7 million people are daily exposed to health risks as a result of use of polluted surface water, besides the additional population in cities like Ota, who due to the failure of Municipal Water Authorities, also rely on surface water sources. Certain findings also show that over 25,000 people die daily all over the world from water-related diseases and that 1.5 billion people lack access to safe water supplies (Peace corps, 2006). This represents a quarter of world population. It is also estimated that each day, over 1 billion people will make a three hour journey on foot just to collect water, yet there is enough water on earth to cover the United States with a blanket 150kilometers thick (Peace corps, 2006).
Ota is an urban area and the fourth largest city in Ogun State, next to Abeokuta, Ijebu-ode and Sagamu. It had a population of 103, 332 during the 1991 census (Iroham, 2005). This shows that it has an estimated current population of 158, 659 using 2.9% growth rate. The city is located between Latitude 60 30’N-60 50’N and longitude 30 02’E-30 25’E, with a height above sea level of 53m. Some of the rivers traversing it include River Iju, River Imojiba, River Ogun, River Abesan and River Illo (see figure 1.1). The river under study is the River Illo. Some segments of the river pass through the Dalemo area of the city and on to the tollgate. As a matter of fact, the river serves as the geographical demarcation between Lagos and Ogun States. People reside along and make use of the water from the river. In the process, they pollute the river. This study undertook the assessment of the water quality in that particular segment of the river with specific interest in an abattoir found along the route of study. An assimilative capacity study of the river to specific pollutants of concern discharged into it from the abattoir was then carried out. Also, contamination levels of the pollutants were determined and compared with FEPA, 1991 and WHO standards (Chapman, 1992) in order to establish the percentage compliance.
1.2 General Description of River Illo
The river Illo runs along the Lagos-Ogun boundary for about 24 kilometers (figure 1.1). It is a perennial river. Some rivers empty into it among which is river Abesan. The river takes its origin in an uninhabited area not far from Itoki town within Ota and passes Ayetoro and Itele communities. The segment of the river that was explored during the field survey was about 0.1m at the shallowest part and 1.5m at the deepest part. In the course of this study, about two kilometers (2km) distance along the route of the river was covered on foot in order to investigate the sources of pollution and water uses.
1.2.1 Identified Sources of pollution
Some of the sources of pollution that were identified include:
•    Fish farm feed and effluents– two of such farms were identified and they are located at approximately 1kilometer from each other. One of the farms had retaining walls (a reinforced concrete structure) right inside the river in order to create a deep pond/reservoir. The fish propagation activities, which include the deposit of feeds rich in nitrogen and phosphorus as well as farm effluents are thus directly disposed into the river body.
 •    Cold room effluents – one cold room facility was identified. It also empties its wastes, which include fish and meat blood that drain from their merchandise, into the river.
•    Abattoir effluents– here, an average of 15 cows, 20 sheep and goats are slaughtered daily, six days in a week (Monday to Saturday). There are no pre-treatment facilities for the wastes before discharge. However, because of the distance of the abattoir discharge point from the water body (about 10m), the formation of a natural pond has taken place. This performs the function of an anaerobic pond, which helps to neutralize much of the concentration of the pollutants, which include fresh blood, paunch wastes, bits and pieces of flesh and splintered bones. Some distance downstream from the slaughter slab, the processing of the beef takes place. This activity generates soot from roasted skin, much of which ends up being emptied into the river body (Plate 6).
•    Domestic wastes - They include wastewater from clothes washing, bathrooms and kitchens. Several enclosures made with wood and corrugated iron sheets (to create some privacy) were identified. Within these enclosures, human faeces are released. Many also throw solid wastes, which consist of food wastes and other wastes, in the absence of alternative means of waste disposal into the river.
1.2.2 Water Uses and Conflict
The water from River Illo within the segment under study is put to
•    Domestic uses – such as bathing and washing. Most people dug well from where they take water for drinking and food processing. They are however ignorant of the fact that the well and river that are at such close proximity affect each other pollution wise through groundwater flow.
•    Fish farms – this is one of the most noticeable activities along the river. Many enterprising citizens simply see the presence of the river as a provision of nature of which they must take advantage.
•    Car washes – only one such facility was observed
  •    Irrigation of gardens – quite a number of households maintain gardens and miniature crop farms along and around the river.
•    Religious rites – about three locations of such practices, especially by Celestial church worshippers who believe in washing their devotees in the river (a form of baptism also practiced by other churches) were observed.
•    Construction work – quite a large number of construction sites were observed whose major or only source of water supply is from the river.
•    Recreation purposes – neighborhood children use the water for recreation activities such as swimming etc
Evidently, there are conflicts in water usage because of the different quality of water required for the different users. Those who use the water for domestic purposes such as cooking and bathing as well as those who use it for religious purposes that involves skin contact with the water will definitely be adversely affected by the effects of discharged blood from cold rooms and abattoirs. Likewise, domestic and human wastes that are emptied into the river poses a danger of high BOD and lowered dissolved oxygen to fish farmers who require that the water be unpolluted.
1.3 Statement of the Problem
Like all rivers passing majorly through densely populated and built environments like Lagos and Ogun States, River Illo has potential for pollution arising from anthropogenic activities. As a result of the high population density, water and sanitation infrastructure are inadequate, hence, rivers like Illo become receiving medium for wastes. The river is used to dispose wastes while at the same time, but at different locations, water is drawn for their domestic use from the same river. This is generally done out of ignorance because the River Illo at times appear clean. The residents along a particular segment of the river simply demarcate a portion of the river that is relatively upstream with respect to their position and draw the water for their domestic uses from this portion. Then, they empty their wastes in the portion they consider as downstream. The unfortunate thing is that someone’s upstream water source is another person’s downstream waste disposal point. Few people bother at all to identify what sorts of wastes are being discharged upstream, the volume of the waste, the ability of the river to cleanse itself before getting downstream to the next user etc. This becomes a major threat to public health.
 1.4 Justification of the study
A general dearth of the much required potable water that satisfies WHO and FEPA standards has made people to resort to scavenging for alternatives, be it ground or surface water. While some dig for water in the vicinity of the river (Plate 1), others use water drawn from the river directly. Both categories of people are at risk as revealed by previous studies (Sangodoyin et al, 1992). While some people draw water from the river for various uses, others dump their wastes into the river, thus using the river as a waste disposal facility. This conflict arising from the diverse interests and uncoordinated activities of people (which includes commercial ventures) has put a large proportion of the consumers of the products of the water from the river at high health risks. However, one cannot entirely sacrifice commercial activities (which translates to economic growth) because of their effluents discharge alone. This is where the need for regulation comes in. However, regulations cannot be formulated without the scientific study of the river, the type and concentration of the pollutants discharged into it, the economic advantages of the activities of commercial users and the future potential uses to which the river can be put (Anyata et al, (2000). The study therefore is to look into the impact of raw effluents being discharged at different points along the river course, taking abattoir effluents as the case study.
Among all the sources of pollution of River Illo that have been identified and enumerated, the most potent pollution is the abattoir effluent discharge. This is because of its high organic content, its concentrated discharge and the volume of waste generated daily. The abattoir was thus adopted as the case study.
1.5 Objectives of the Study
The objectives of the present study are:
1.    To identify the various uses to which the river Illo in Ota, Ogun State, Nigeria is being put.
2.    To evaluate the impact of the abattoir effluent discharge on the river and consequently, the risk posed to public health as a result of the identified pollution.
3.    To measure the level of pollution from disposal of abattoir effluents into the river.
4.    To model the dispersion factor and dissolved oxygen characteristic of the river as it relates to the abattoir effluent discharge.
5.    To determine the capacity of the river to cleanse itself from its pollutants
 1.6 Expected Contribution To Knowledge
The study will provide basic information on the water use and conflict. It will also evaluate the current water quality and degree of pollution of the river. The data will furnish information that will be useful to predict likely changes over time in the concentration levels of different pollutants. Possible solutions to the existing problems will be suggested and may form basis of adoption of engineering measures to arrest river pollution by commercial and industrial activities.
1.8 Scope of the study
The study consisted of a field survey, sampling exercise, a laboratory analysis of samples obtained and an interpretation of laboratory data using statistical, graphical and established modeling tools. The field survey was carried out over a two-kilometer distance of the river within Ota (specifically between Dalemo and Tollgate area). The sampling exercise, however, was done over 110m-distance. Taking the abattoir discharge point as the source, six grab samples of water were obtained from the source and downstream of the discharge point. The seventh sample was taken 10meters upstream to reflect the ambient value of the river before pollution. An eighth sample which was prepared by diluting water obtained at 0m with distilled water (i.e. 25% stream water, 75% distilled water) was included to serve as control sample.