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
11  Background Information       1                             
12   Water Quality modelling       3
13   Description of Study Location     5
14   Statement of The Problem      6
15   Aim         6
16   Objectives        6
17   Significance of Study       6
18   Scope of Study       7
 
   CHAPTER TWO: LITERATURE REVIEW
21  Water Quality Modelling as a Field of Study    8
22   Coefficient of Re-aeration, k2      9
223  The Indian k2 Model       13
224  The Chilean k2 Model       14
225  The Nigerian k2 Model     15
23    Water Laws and Standards       15
24    Statistical Analysis       17
241  Some Relevant Statistical Operations   17
242  Statistical Software     19
243  Model Calibration and Validation in Water Quality
Data       20
2431      Sum of Squares Due to Error  21
2432      R-Square        21
2433      Degrees of Freedom Adjusted R-Square 22
2434      Root Mean Squared Error   22
 
CHAPTER THREE: METHODOLOGY  
        31   Selection of the Study Area       24
       32   Determination of Sampling Stations      27
       33   Field Activities        49
  331  Field Observations      31
  332  Field Sampling Visits      31
   3321     Rationale for Gathering Data Once Every Month  32
    3322     Activities During the Field Exercises  33
            34     Materials        34
            3

5     Laboratory Analysis       36
       36     Data Analysis        37
            361    Time of Travel       38
           362    Re-aeration Coefficient Model     39
 
CHAPTER FOUR: DATA PRESENTATION AND INTERPRETATION
  41 Data Gathering       40
   411   Hydraulic Data      41
   412   Physico-Chemical Data     50
    413  Monthly Variations in DO, Temperature, Stream Depth       57
   42  Computation of Measured k2                                                              63
            43  Re-arrangement of Sampling Stations    67
431  Time of Travel      68
432  Hydraulic Radius                 80
433  Ultimate BOD and De-oxygenation Rate              80
434  Saturation DO and the Upstream and Downstream DO deficits  80
 435  Determination of k2                 80
436  Model Parameters                 80
437  The Model                  83
438  Comparison with other Selected Models              83
44  Water Use Practices                             103
 45       Pollutants and Public Health Implications              106
 
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION
51  Conclusion                  110
52 Contribution to Knowledge                111
53  Recommendations                 111
       
REFERENCES                   113
 
APPENDICES  
Appendix 1: Matlab Code for Beta               121
Appendix 2: Matlab Model Output                          128
Appendix 3: Matlab Code and Output for Plot of all Models           132
Appendix 4: Mix Calculations               140
Appendix 5: Laboratory Reports               147  
Appendix 6: Procedure for data Analysis              160

LIST OF FIGURES                                           PAGE
Figure 11 – Nigerian Household distribution by source of water supply  2
Figure 12 – Nigerian Household distribution by Toilet Facilities   3
Figure 13 â“ General Layout of the Study area     5
Figure 31â“ Field Sampling Stations       28
Figure 32 â“ Linear representation of Sampling Points    29
Figure 33 – Sampling Cross-section       33
Figure 41 â“ An 8-month mean stream velocity record    59
Figure 42 â“ An 8-month mean ambient temperature record    60
Figure 43 â“ An 8-month mean water temperature record    61
Figure 44 â“ An 8-month mean stream depth record      61
Figure 45 â“ DO Fluctuations over an 8-month period    62
Figure 46 – Flowchart showing the progression of the statistical analysis            86
Figure 47 â“ Plot of 11 models using January data                93
Figure 48 â“ Plot of measured k2 against computed k2 using January data            94
Figure 49 â“ Plot of 11 models using March data                96
Figure 410 – Plot of measured k2 against computed k2 using March data            97
Figure 411 â“ Plot of 11 models using July data                99
Figure 412 – Plot of measured k2 against computed k2 using July data            100

LIST OF TABLES                                                                                  PAGE
 
Table 21 â“ The self-purification factor, f, of different water bodies at 20oC  9
Table 22 â“ Solubility of Oxygen in water      10
Table 31 – Details of Sampling Stations      30
Table 32 â“ Parameters Measured with Relevance to study    32
Table 33 â“ Parameters, equipment and Processes of  parameter determination
Schedule for field work        34
Table 41 – Sampling dates and conditions      40
Table 42a â“ Hydraulic Data for January      42
Table 42b â“ Hydraulic Data for February      43
Table 42c â“ Hydraulic Data for March      44
Table 42d â“ Hydraulic Data for April      45
Table 42e â“ Hydraulic Data for May       46
Table 42f â“ Hydraulic Data for July       47
Table 42g â“ Hydraulic Data for August      48
Table 42h â“ Hydraulic Data for September      49
Table 43a â“ Physico-Chemical Parameters for January    50
Table 43b â“ Physico-Chemical Parameters for February    51
Table 43c â“ Physico-Chemical Parameters for March     52
Table 43d â“ Physico-Chemical Parameters for April     53
Table 43e â“ Physico-Chemical Parameters for May      54
Table 43f â“ Physico-Chemical Parameters for July      55
Table 43g â“ Physico-Chemical Parameters for August    56
Table 43hâ“ Physico-Chemical Parameters for September    57
Table 44 â“ Mean Monthly Ambient and Water Temperatures   60
Table 45 â“ Determination of Reaches for the River      64
Table 46 – Dilution Effects for January      65
Table 47 – Dilution Effects for February      65
Table 48 – Dilution Effects for March      65
Table 49 – Dilution Effects for July       66
Table 410 – Dilution Effects for August      66
Table 411 – Dilution Effects for September      66
Table 412 â“ Re-arrangement of station numbers      67
Table 413 â“ Computation of time of travel on Programmed Excel Spreadsheet for January          68
Table 414 â“ Computation of time of travel on Programmed Excel Spreadsheet for
February          69
Table 415 â“ Computation of time of travel on Programmed Excel Spreadsheet for
March           70
Table 416 â“ Computation of time of travel on Programmed Excel Spreadsheet for
July           71
Table 417 â“ Computation of time of travel on Programmed Excel Spreadsheet for
August                      72
Table 418 â“ Computation of time of travel on Programmed Excel Spreadsheet for
September                     73
Table 419 â“ Computation of k1 and k2 on Programmed Excel Spreadsheet for JanuaryTable 420 â“ Computation of k1 and k2 on Programmed Excel Spreadsheet for
February                     75
Table 421 â“ Computation of k1 and k2 on Programmed Excel Spreadsheet for March
                      76
Table 422â“ Computation of k1 and k2 on Programmed Excel Spreadsheet for July
                                          77
Table 423 â“ Computation of k1 and k2 on Programmed Excel Spreadsheet for August
                                 78
Table 424 â“ Computation of k1 and k2 on Programmed Excel Spreadsheet for
September                     79
Table 425â“ Model fit and goodness of fit Summary for Dry Season              81
Table 426â“ Model fit and goodness of fit Summary for Rainy Season           82
Table 427 â“ Selected Models for Model Validation (Test of performance)    84
Table 428â“ Goodness of fit using January Data                 91
Table 429- Goodness of fit using March Data                 91
Table 430- Goodness of fit using July Data                            92
Table 431: Graphical Goodness of fit using January, March and July Data  102
Table 432 â“ Order of Composite Goodness of Fit               103
Table 433 â“ Comprehensive River water and Industrial Effluent Analysis   107
LIST OF PLATES                                            PAGE
Plate 31 â“ The industrial effluent flowing along the road down towards the river 25
Plate 32 â“ the effluent accumulates (left) from where it seeps into the river body 25
Plate 33 â“ Effluent accumulation beside the river body    26
Plate 34 â“ Villagers of Iju tapping the river water for domestic use   26
Plate 35 â“ Sewage being taken near the river for disposal    27
Plate 36 â“ Field pH meter        35
Plate 37 â“ Eurolab digital thermometer with sensitive probe   35
Plate 38 – Geopacks Stream flow sensor with its pole and fan-like impeller  36
Plate 39 – Measuring the river width with a tape      36
Plate 310 â“ the Speedtech Portable Depth Sounder (yellow torchlight shaped
instrument)          57
Plate 41 â“ Sampling Station 10 in Rainy season (August)    58
Plate 42 â“ Sampling Location 10 in Dry season (March)    58
Plate 43 â“ Human skeleton found in the River               104
Plate 44 â“ Pollution along the river channel                          104
Plate 45 â“ The research team could not proceed because of blockage of the river  105
Plate 46 â“ Water intake station for Ogun State Water Corporation                        105
Plate 47 â“ Man swimming after the dayâs work               106

ABBREVIATIONS AND SYMBOLS
1  DO â“ Dissolved Oxygen
2  BOD –  Biochemical Oxygen Demand
3  QUAL â“ Stream Water Quality models
4  CORMIX â“ Cornell Mixing Zone Expert
5  WASP â“ Watershed Quality Analysis Simulation Programme
6  FEPA â“ Federal Environmental Protection Agency
7  USEPA â“ United States Environmental Protection Agency
8  USGS â“ United States Geological Society
9  UNESCO â“ United Nations Education, Scientific and Cultural Organization
10 DV â“ Dependent Variable
11 IV â“ Independent Variable
12 ANOVA â“ Analysis of Variance
13 SSE â“ Error Sum of Squares
14 SSR â“ Residual sum of squares
15 SST â“ Total sum of squares
16 R2 â“ correlation coefficient
17 Adj R2â“ Adjusted Correlation coefficient
18 RMSE â“ Root mean square error
19 APHA – American Public Health Association
20 SPSS â“ Statistical Package for Social Sciences
21 MATLAB â“ Matrix Laboratory software
22 GPS â“ Global Positioning System
23 k2 â“ re-aeration coefficient
24 k1 â“ de-oxygenation coefficient
25 f â“ self purification factor
26 2 ^Ï  – estimated variance
27 mg/l â“ milligram per litre