EVALUATION OF WATER QUALITY MODELLING PARAMETERS: TOWARDS THE EVOLVEMENT OF RE-AERATION COEFFICIENT FOR RIVERS IN THE NIGERIAN ENVIRONMENT

ABSTRACT 
This study was carried out on River Atuwara in Ota, Ogun State, Nigeria with the aim of developing a coefficient of re-aeration model applicable to River Atuwara and other rivers in the Nigerian environment. This was achieved by sourcing for data once every month from 22 sampling locations of interest within a pre-selected segment of the river over a period covering the dry and wet seasons. The data collected include hydraulic data (depth, width, velocity and time of travel) and water quality data such as Dissolved Oxygen (DO) and Biochemical Oxygen Demand (BOD). Excel Spreadsheet and MATLAB were used for data processing. Regression analysis was carried out where stream velocity and depth were the regressors and the re-aeration constant k2 (as a function of BOD, DO and Temperature) was the dependent variable.  A coefficient of re-aeration, k2, (Atuwara re-aeration model) was developed and validated statistically. Its performance was also verified by comparing the model with 10 other internationally recognized models. It was  found that even though Atuwara model performed better than Agunwamba model and most of the other well cited models, both Atuwara model and Agunwamba model could be safely adopted for future water quality modelling researches in the Nigerian environment.  Results of detailed water analysis of samples from River Atuwara shows high level of pollution hence it is unfit for human consumption without adequate treatment. It is recommended that River Atuwara and similar rivers in the country should be regularly monitored for quality control.

TABLE OF CONTENTS      PAGE 
Title Page          i  
Declaration         ii  
Certification         iii 
Dedication          iv 
Acknowledgement        v 
Table of Contents         vii 
List of Figures         x 
List of Tables         xi 
List of Plates         xiv 
Abbreviations and Symbols       xv 
Abstract          xvi 
 
CHAPTER ONE: INTRODUCTION 
1.1  Background Information       1                             
1.2   Water Quality modelling       3 
1.3   Description of Study Location     5 
1.4   Statement of The Problem      6 
1.5   Aim         6 
1.6   Objectives        6 
1.7   Significance of Study       6 
1.8   Scope of Study       7 
 
   CHAPTER TWO: LITERATURE REVIEW 
2.1   Water Quality Modelling as a Field of Study    8 
2.2   Coefficient of Re-aeration, k2      9 
2.2.3  The Indian k2 Model       13 
2.2.4  The Chilean k2 Model       14 
2.2.5  The Nigerian k2 Model     15 
2.3    Water Laws and Standards       15 
2.4    Statistical Analysis       17 
2.4.1  Some Relevant Statistical Operations   17 
2.4.2  Statistical Software     19 
2.4.3  Model Calibration and Validation in Water Quality Data       20 
2.4.3.1      Sum of Squares Due to Error  21 
2.4.3.2      R-Square        21 
2.4.3.3      Degrees of Freedom Adjusted R-Square 22 
2.4.3.4      Root Mean Squared Error   22 
 
CHAPTER THREE: METHODOLOGY  
        3.1   Selection of the Study Area       24 
       3.2   Determination of Sampling Stations      27 
       3.3   Field Activities        49 
  3.3.1  Field Observations      31 
  3.3.2  Field Sampling Visits      31 
   3.3.2.1     Rationale for Gathering Data Once Every Month  32 
    3.3.2.2     Activities During the Field Exercises  33 
            3.4     Materials        34 
            3.5     Laboratory Analysis       36 
       3.6     Data Analysis        37 
            3.6.1    Time of Travel       38 
           3.6.2    Re-aeration Coefficient Model     39 
 
CHAPTER FOUR: DATA PRESENTATION AND INTERPRETATION 
  4.1 Data Gathering       40 
   4.1.1   Hydraulic Data      41 
   4.1.2   Physico-Chemical Data     50 
    4.1.3  Monthly Variations in DO, Temperature, Stream Depth       57 
   4.2  Computation of Measured k2                                                              63 
            4.3  Re-arrangement of Sampling Stations    67 
4.3.1  Time of Travel      68 
4.3.2  Hydraulic Radius                 80 
4.3.3  Ultimate BOD and De-oxygenation Rate              80 
4.3.4  Saturation DO and the Upstream and Downstream DO deficits  80
 4.3.5  Determination of k2                 80 
4.3.6  Model Parameters                 80 
4.3.7  The Model                  83 
4.3.8  Comparison with other Selected Models              83 
4.4  Water Use Practices                             103 
 4.5       Pollutants and Public Health Implications              106 
 
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION 
5.1  Conclusion                  110 
5.2 Contribution to Knowledge                111 
5.3  Recommendations                 111 
       
REFERENCES                   113