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NATIONAL OPEN UNIVERSITY OF NIGERIA
SCHOOL OF SCIENCE AND TECHNOLOGY
COURSE CODE: EHS 304
COURSE TITLE: HYDROLOGY AND SANITATION
EHS 304 MODULE 3
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EHS 304
HYDROLOGY AND SANITATION
Course Team Jonas O. Okwa (Course Developer/Writer)
Environmental Health Department
Ministry of Environment and Mineral Resources,
Enugu
Prof. Afolabi Adebanjo (Programme Leader) –
NOUN
Dr. Shehu Omoniyi Ibrahim (Course Coordinator) -
NOUN
NATIONAL OPEN UNIVERSITY OF NIGERIA
COURSE
GUIDE
86
National Open University of Nigeria
Headquarters
14/16 Ahmadu Bello Way
Victoria Island, Lagos
Abuja Office
5 Dar es Salaam Street
Off Aminu Kano Crescent
Wuse II, Abuja
e-mail: [email protected]
URL: www.nou.edu.ng
Published by
National Open University of Nigeria
Printed 2014
ISBN: ISBN: 978-058-198-7
All Rights Reserved
EHS 304 MODULE 3
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CONTENTS PAGE
Introduction ……………………………………………….. iv
What you will Learn in this Course ……………………… iv
Course Aim………………………………………………… iv
Course Objectives …………………………………………. iv
Working through this Course ……………………………… v
Course Materials …………………………………………… v
Study Units …………………………………………………. v
Textbooks and References ………………………………… vi
Presentation Schedule …………………………………….. vi
Assessment ……………………………………………… vi
Tutor-Marked Assignments ……………………………… vii
Final Examination and Grading …………………………… vii
Course Marking Scheme ………………………………….. vii
Facilitators, Tutors and Tutorials ………………………… vii
Summary ………………………………………………… viii
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INTRODUCTION
Hydrology and sanitation is a semester course. It is a two-credit unit
course available to all students of Bachelor of Science degree in
Environmental Health.
Hydrology is the arm of science that deals with occurrence, movement,
distribution and storage of water in respect to both its quantity and
quality over and below the land surface in space, time and frequency
domain. Sanitation on its own is the hygienic means of promoting
heath through prevention of human contact with the hazards of
wastes.
Water is an indispensable gift from God because of its uses. Its
application to sanitation is a sine qua non because without it one can
hardly talk of sanitation. Water itself needs adequate sanitation so as
not to turn all its inherent uses sanitation-wise into curses which it
equally has in abundance if not well treated.
WHAT YOU WILL LEARN IN THIS COURSE
This course guide explains to you what to expect from reading the
course material, the materials you need and how to work with them.
In the course material, you will learn about water occurrence, cycle,
movement and distribution as well as its supply to people. Also to be
learnt is sanitation and its branches and application to water
treatment. Tutor-marked assignments will also be seen and are
expected to be done by you. Finally it is expected that the course will
prepare you for challenges you are likely to meet in the study of
environmental health.
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COURSE AIM
The aim of this course is to provide you with a good understanding of
hydrological processes and how it affects and is being affected by
sanitation for better management of water and our environment.
COURSE OBJECTIVES
After going through this course, you should be able to:
define and explain the concepts and theories of hydrology
give the classifications and application of hydrology and explain the hydrological cycle
explain environmental problems of urbanisation and natural cycle of water
discuss physical, chemical and biological principles of wastewater and water treatment
explain the application of sanitation to water and water to sanitation
discuss sources of water, its supply and distribution and its environmental problems
explain the procedures for water sampling techniques
discuss urban and community storm water management process
explain drainage system layout and its importance
explain the state and federal regulatory standards and the role such play in water supply and sanitation.
WORKING THROUGH THIS COURSE
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This course has been carefully put together bearing in mind that you
might be new to the course. However, efforts have been made to
ensure that adequate explanation and illustrations are made to
enhance better understanding of the course. You are therefore advised
to spend quality time to study this course and ensure that you attend
tutorial sessions where you can ask questions and compare your
knowledge with that of your colleagues. Each unit contains self-
assessment exercise. You would be required also to submit your
assignments for assessment. This course should take about 15 weeks to
complete.
COURSE MATERIALS
The main components of the course materials are:
Course Guide
Study Units
References/Further Reading
Assignments File
STUDY UNITS
This course is divided into 15 units discussed under 3 modules as given
below:
Module 1
Unit 1 Definitions, Concepts and Theories of Hydrology
Unit 2 Elementary Hydrology
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Unit 3 Hydrological Cycle
Unit 4 Environmental Problems of Urbanisation and Natural
Cycle of Water
Unit 5 Physical, Chemical and Biological Principles of
Wastewater Treatment
Module 2
Unit 1 Definitions, Concepts, Theories of Sanitation and
Application of Water to Sanitation
Unit 2 Sources of Water and its Protection
Unit 3 Water Sampling Techniques
Unit 4 Water Supply and Distribution
Unit 5 Environmental Problems of Water Supply and Distribution
Module 3
Unit 1 Physical, Chemical and Biological Principles of Water
Treatment
Unit 2 Public Health Importance of Water
Unit 3 Urban and Community Storm Water Management
Unit 4 Drainage Layout
Unit 5 State and Federal Regulation Standards
TEXTBOOKS AND REFERENCES
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You are advised to consult as many textbooks /journals/ internet
sources contained at the end of every unit for a good understanding of
this course.
PRESENTATION SCHEDULE
Your course materials have important dates for the early and timely
completion and submission of your TMAs and tutorial attendance. You
are expected to submit all your assignments by the stipulated time and
date and guard against falling behind in your work.
ASSESSMENT
There are three parts to the course assessment and these include self-
assessment exercise, tutor- marked assignments. In tackling the
assignments, you are expected to use the information, knowledge and
techniques gathered during the course. The assignments must be
submitted to your facilitator for marking in line with the timelines
stated in the presentation schedule and assignment file. The
assignment that you submit to your tutor for assessment will count for
30% of your total course work. At the end of the course you will need
to sit for a final end of course examination of about three hours
duration. This examination will count for 70% of your total course
mark.
TUTOR-MARKED ASSIGNMENTS (TMAs)
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The TMA is a continuous component of your course. It accounts for
30% of the total score. You will be given four TMAs to answer. Three of
this must be answered before you are allowed to sit for the end of
course examination. The TMAs would be given to you by your facilitator
and returned after you have done the assignment. Assignment
questions for the units in this course are contained in the assignment
file. You will be able to complete your assignment from the information
and material contained in your reading, references and study units.
However, it is desirable in all degree level of education to demonstrate
that you have read and researched more into your references, which
will give you a wider view point of the subject.
Make sure that each assignment reaches your facilitator on or before
the deadline given in the presentation schedule and assignment file. If
for any reason you cannot complete your work on time, contact your
facilitator before the assignment is due; discuss the possibility of an
extension. Extension will not be granted after the due date unless there
are exceptional circumstances.
FINAL EXAMINATION AND GRADING
The end of course examination for EHS 304 will be for about three
hours and it has a value of 70% of the total course work. The
examination will consist of questions, which will reflect the self-
assessment, practice exercise and tutor-marked assignment problems
you have previously encountered. All areas of the course will be
assessed, therefore, use the time between finishing the last unit and
sitting for the examination to revise the whole course. You might find it
useful to review your self-assessment, TMAs and comments on them
before the examination. The end of course examination covers
information from all parts of the course.
COURSE MARKING SCHEME
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Assignment Marks
Assignments 1-4 Four assignments, best three of
the four count 30% course marks
End of course examination 70% of overall course marks
Total 100% of course materials
FACILTATORS, TUTORS AND TUTORIALS
There are 15 hours of tutorials provided in support of this course. You
will be notified of the dates, times and location of the tutorials as well
as the name and the phone number of your facilitator, as soon as you
are allocated a tutorial group.
Your facilitator will mark and comment on your assignments, keep a
close watch on your progress and any difficulties you might face and
provide assistance to you during the course. You are expected to mail
your tutor-marked assignment to your facilitator before the schedule
date (at least two working days are required). They will be marked and
returned to you as soon as possible.
Do not delay to contact your facilitator by telephone or e-mail if you
need assistance.
The following might be circumstances in which you would find
assistance necessary, hence you would have to contact your facilitator
if you:
EHS 304 MODULE 3
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do not understand any part of the study or the assigned readings
have difficulty with self-assessment exercise
have a question or problem with an assignment or with the grading of an assignment.
You should endeavour to attend the tutorials. This is the only chance to
have face- to-face contact with your course facilitator and to ask
question which are answered instantly. You can raise any problem
encountered in the course of your study.
To gain more benefit from course tutorials prepare a question list
before attending them. You will learn a lot from participating actively in
discussions.
SUMMARY
This course intends taking you into an in-depth study on hydrology and
sanitation. Hydrology on itself means the study of water and its allied
attributes- occurrence, movement, distribution, quantity and quality
within a specified time and space. Sanitation on its own mean all those
measures employed and aimed at taming our environment so that it
does not become a threat to man. To harness all the usefulness of
water, it must be supplied and distributed in good, safe and adequate
manner and must be made to serve the urban and local areas.
Water which is cyclic in nature is an indispensable tool in achieving
environmental sanitation. Apart from structural provisions made to
achieve some good health, most of other aspects of achieving
environmental sanitation come through the use of water. On its own,
water itself needs adequate sanitation for it to perform its roles. If
neglected water related diseases will ensue and make a mess of man
and his water. To help use water well, regulatory standards are laid by
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local, state and federal government. You cannot but jump into reading
so as to see all these.
We sincerely wish you happy reading
Good Luck.
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CONTENTS
PAGE
Module 1 Conceptual and Theoretical
Framework on Hydrology………………. 1
Unit 1 Definitions, Concepts and
Theories of Hydrology………………........ 1
Unit 2 Elementary Hydrology …………………… 9
Unit 3 Hydrological Cycle……………………… 16
Unit 4 Environmental Problems of Urbanisation
and Natural Cycle of Water……………… 23
Unit 5 Physical, Chemical and Biological Principles
of Wastewater Treatment…………………… 33
Module 2 Water Sanitation and Municipal Services… 41
Unit 1 Definitions, Concepts, and Theories of Sanitation
and Application of Water to Sanitation……… 41
Unit 2 Sources of Water and its Protection………. 49
Unit 3 Water Sampling Techniques………………. 58
Unit 4 Water Supply and Distribution………….… 66
Unit 5 Environmental Problems of Water
Supply and Distribution……………………. 78
MAIN
COURSE
98
Module 3 Public Health Importance of Water,
Drainage Layout
and Regulatory Standards……………… 84
Unit 1 Physical, Chemical and Biological
Principles of Water Treatment……………… 84
Unit2 Public Health Importance of Water………. 96
Unit 3 Urban and Community Storm Water Management 107
Unit 4 Drainage Layout…………………………….. 118
Unit 5 State and Federal Regulatory Standard……… 130
MODULE 1 CONCEPTUAL AND THEORETICAL
FRAMEWORK OF HYDROLOGY
Unit 1 Definitions, Concepts and Theories of Hydrology
Unit 2 Elementary Hydrology
Unit 3 Hydrological Cycle
Unit 4 Environmental Problems of Urbanisation and Natural
Cycle of Water
Unit 5 Physical, Chemical and Biological Principles of
Wastewater Treatment
UNIT 1 DEFINITIONS, CONCEPTS AND THEORIES
OF HYDROLOGY
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Definitions of Hydrology
3.2 Concepts of Hydrology
3.3 Theories of Hydrology
3.3.1 Uses of Catchment Theory of Hydrology
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4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/ Further Reading
1.0 INTRODUCTION
It is a known fact that if the whole world is divided into ten, water
bodies (hydrosphere) occupy 70 per cent leaving only 30 per cent for the
solid earth (lithosphere) (Goh Cheng, 1971). Greater percentage of this
water is found in the oceans. The result is that the world does not have
equal distribution of water and yet everything and everybody under the
earth need water. More so, since creation, there has been a fairly
constant volume of water in circulation in this world irrespective of
time, variations in seasons and geographical differences.
This unit therefore, is concerned with the study of water availability,
quality and distribution.
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2.0 OBJECTIVES
At the end of this unit, you should be able to:
define hydrology
explain concepts of hydrology
discuss theories of hydrology.
3.0 MAIN CONTENT
3.1 Definitions of Hydrology
Hydrology is from the Greek words “hydor” (water) and ‘Logos’ (study)
to mean “the study of water”. Below are however some true definitions
of hydrology.
According to Wikipedia, hydrology is the study of movement,
distribution and quality of water on earth and other planets, including
the hydrologic cycle, water resources and environmental watershed
sustainability. A practitioner of hydrology is a hydrologist, working
within the fields of earth or environmental science, physical geography,
geology or civil and environmental engineering.
Singh (2000) asserts that hydrology can be defined as the science that
deals with occurrence, movement, distribution and storage of water in
respect to both its quantity and quality over and below the land surface
in space, time and frequency domains. Water quantity encompasses the
physical aspects and water quality, the chemical and biological aspect.
The author concludes by saying that one might sum up hydrology as the
study of water in all aspect at macro and higher scales. From the above,
one can freely say that hydrology is the study of the occurrence,
distribution, movement and physical and chemical properties of water in
Earth’s atmosphere, surface, and near-surface crust.
3.2 Concepts of Hydrology
Water is a liquid with all the characteristics of a liquid, one of which
include possession of a definite volume but no definite shape. Thus, it
takes the shape of the container. Also, water always findings its level. It
can exist in three phases- solid, liquid and gaseous (ice, liquid and water
vapour) respectively which change their phase through the following
processes:
from solid (ice) to liquid (water) termed melting process and
from liquid (water) to solid (ice) termed freezing process
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from liquid (water) to gas (water vapour) termed
vaporisation/evaporation process and from gas (water vapour) to
liquid (water) termed condensation process
from solid (ice) to gas (water vapour) termed sublimation (+) and
from gas (water vapour) to solid (ice) termed sublimation (-). The
negative (-ve) sublimation is known as deposition.
All the above phenomena are controlled by the vapour pressure and
temperature under which the water is subjected. The above features of
water are contained in the Figures 1.1 and 1.2 below.
Energy is released (-) when hydrogen bonds are formed. Energy is
consumed (+) when hydrogen
bonds are broken:
Fig. 1.1: Water Found in 3 Phases
Source: http:www.sci.uidaho.edu/scripter
102
Fig. 1.2: Vapour Pressure vs. Temperature
Source: http:www.isbu.ac.uk/water/phase.html
Water is a universal solvent and fairly ubiquitous. As a universal solvent
it dissolves organic and inorganic minerals as it moves especially on top
or below the soil. It forms the oceans, rivers, lakes and streams and it is
found in plants, animals and humans and under the solid earth
(Lithosphere). Its quality depends on the level of impurities that
combine with the natural chemical elemental constituents of water
which are hydrogen and oxygen in the radio of 2.1, thus pure water
molecule is H2o. However, it will be observed later that good potable
water has some dissolved salt substances while unwholesome water has
organic, inorganic and pathogens in them.
Hydrological processes arise as a result of interactions between climate
inputs and landscape characteristics that occur over a wide range of
space and timescales. In the time domain, these may range from a few
second needed to capture turbulent exchanges of mass, energy, and
momentum between the land surface and the atmosphere, to
intermediate timescales governing runoff generation process during
storm events, for example, overland flow and sub surface storm flow,
and long timescales governing deep ground water flow, seasons
variations of climate and annual water balances, etc. In the space
domain, the length scales may range from an individual soil pore, leaf
blade or surface gully to small hill slopes, to river basin as large as
Mississippi, to whole climatic or geographical region all the way to the
entire globe.
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3.3 Theories of Hydrology
In the first place, the word “theory” according to Hornsby’s (1998)
Oxford Advanced Learners’ Dictionary means a set of properly argued
ideas intended to explain facts or events; the principles on which a
subject of study is based, among others. The question now is what are
the theories of hydrology?
In the study of hydrology, a lot of theories abound which govern the
processes involved in it as will here-under be seen. According to
Murugesu (2005), hydrology boasts of many theories, for each of its
many consistent processes (example: infiltration, evaporation, overland
flow, ground water flow etc), but there is an almost complete lack of a
holistic theory unique to hydrology itself, unifying these varied theories.
Hydrology is of great importance in the study of earth system, and
deserves to have these theories explained. The theories connected with
the processes, of say, infiltration or evaporation, etc deal with these
processes alone on individual basis, and because of this, it is termed
‘individual process theories” or “small scale process theories.” It is
termed individual process or small scale process theory because each of
them has got its own mechanism of operation. For instance, the
processes involved in evaporation, whereby the relatively stronger force
uniting the top of the surface water with those below loses its power and
allow the escape of water in gaseous form is different from capillary
action of water molecules in the soil that allows percolation or
infiltration and so on.
In spite of the sophistication of the individual process theories there has
been little progress towards understanding the law’s governing the
interactions and feedbacks between these processes so much so that
modules based on “current process theories” were evolved. These
theories discuss the processes hydrological activities take to be effected
and within these current process theories, a new theory called the unified
theory of hydrology is being advocated which unites the individual/
small scale theories and the current process theories. This new unified
theory of hydrology is termed ‘the theory of catchment hydrology”. It is
more coherent and unites other theories as earlier mentioned.
The Catchment Theory of Hydrology
This is an improvement over all other theories and would considerably
improve the understanding of hydrological phenomena, including a
more holistic understanding of their function within the entire earth
system, and improve the management of water resources, water quality
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and water- related natural hazards. It is not heterogeneous or
fragmented as other theories.
Before giving what catchment theory means, it should be understood
that due to the tremendous heterogeneities in landscape properties and
climatic inputs, the resulting hydrological processes are highly variable
and complex of all scales. For instance, it is not practical, or even
feasible to routinely observe hydrological processes at the scale of a soil
pore or a surface gully or at the scale of a hill slope, in all catchments.
By way of definition or explanation, this catchment theory explains the
scale at which routine observations are made and predictions are
possible and required. This is because for both scientific and practical
reasons routine observations of hydrological processes are made only at
the catchment level but not during the individual processes as seen in the
process theory. Catchments thus qualify as complex or poorly defined
systems. This means that while process understanding at all scales
especially at scales smaller than catchment scale, is very valuable in
guiding or underpinning predictions of catchment responses, actual
predictions must still be based and or conditioned on observations at the
catchment scale.
The catchment is a self organising system whose form, drainage
network, ground and channel slopes, channel hydraulic geometries,
soils, and vegetation etc can now be known and its characteristics be
told with ease as against the individual process theory. However, a
holistic theory of hydrology at the catchment scale must be founded on a
synthesis of process understanding and process theories at all scales with
empirical theories derived from the analysis of observations at the
catchment scale.
3.3.1 Advantages or Uses of Catchment Hydrology
1. Catchment integrates all aspects of the hydrological cycle within
a clearly defined area in a way that can be studied, quantified and
acted upon. It is for this reason that we choose catchments as the
building blocks for the development of a new hydrological
theory.
2. Despite varieties of approaches to catchments hydrology,
understanding of the spatial and temporal variability of
hydrological process aggregated to the catchment scale, their
extremes and their scaling behaviour both in time and space has a
number of uses like flood estimation, drought mitigation and
water resources systems analysis. Thus, the pathways that water
takes in its passage through the catchment, their spatial and
temporal variability and the associated residence times are
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important for water quality prediction and for managing the
health of aquatic ecosystems.
3. Improvement to the theory of catchment hydrology will have
positive ramifications beyond hydrology, contributing to the
sustainable management of land and water resources and aquatic
ecosystems and to managing global change.
SELF-ASSESSMENT EXERCISE
What are the theories of hydrology and which of them is the best?
4.0 CONCLUSION
Having gone through all the above, we can conclude by saying that
having a fair knowledge about what hydrology is through the study of its
definitions, concepts, and theories will be of help because of the
importance of water to man. The behaviours of water when existing in
the three phases learnt teach us how to maximise its uses effectively.
Through this study many predictions about water can be made.
5.0 SUMMARY
In this unit, we learnt a lot about the term hydrology. Definitions or the
meaning of hydrology were variously given and all point to the fact that
it is the study of water and its occurrence, movement, distribution,
storage and the quality and quantity of water over and below the surface
in time and space.
The unique substance-water- was diagrammatically studied to show its
triple nature of being in solid, liquid and gaseous state and the effect of
temperature and pressure. Concepts about water were discussed before
dealing with the theories. Under the concepts we learnt about the nature
of water and some of its characteristics.
Just as there are many concepts of hydrology, so also its theories of
which the catchment theory is first.
6.0 TUTOR-MARKED ASSIGNMENT
1. Give the definitions of hydrology and state three reasons why its
study is important.
2. Explain the theories of hydrology.
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7.0 REFERENCES/ FURTHER READING
Dooge, J.C.I. (1986). “Looking for Hydrologic Laws.” Water Resources
Research, 22 (9) 465-585.
Dune, T. (1998). “Wolman Lecture: Hydrologic Science in Landscapes
on a Planet in the Future.” Hydrologic Science: Taking Stock and
Looking Ahead. Washington: National Academic Press.
Goh, C. L. (1971). Certificate Physical and Human Geography.
London: Oxford University Press.
Lucas, A. O. & Gilles, H. M. (1984). A Short Textbook on Preventive
Medicine for the Tropics. London: Hodder and Stoughton.
Murugesu, S. (2005). “Pattern, Process and Function: Elements of a
Unified Theory and Hydrology at the Catchment Scale.” In: M.
G. Anderson. (Ed.). Encyclopedia of Hydrological Sciences.
Australia: John Wiley and Sons Ltd.
Singh, V. P. (2000). “Hydrology” The Engineering Handbook. Boca
Raton: CRC Press LLC.
“Water a Unique Substance.” http:www.sci.uidaho.edu/scripter.
Accessed 24/08/2012.
www.isbu.ac.uk//water/phase.html
EHS 304 MODULE 3
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UNIT 2 ELEMENTARY HYDROLOGY
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Meaning of Hydrology and its Historical Perspective
3.2 Classifications/Branches and Hydrology
3.3 Application of Hydrology
3.3.1 Application of Hydrological Knowledge in Nigeria
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/Further Reading
1.0 INTRODUCTION
In unit 1, you were introduced to the study of hydrology where you
learnt that it is an arm of science that deals with occurrence, movement,
distribution and storage of water in respect to both quantity and quality
over and below the land surface in space, time and frequency domains.
The study of hydrology is of great importance as there are many uses or
applications to human society. We have several branches of hydrology.
In this unit, we shall look into elementary hydrology with emphasis on
the meaning of hydrology, its classifications/branches and the
application of hydrology in general and the application of hydrological
knowledge in Nigeria.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
explain brief history of hydrology
discuss classification of hydrology
explain application of hydrology
describe application of hydrology in Nigerian context.
3.0 MAIN CONTENT
3.1 Meaning of Hydrology and its Historical Perspective
The central theme of hydrology is that water circulates throughout the
earth through different pathways and at different rates. The study of the
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hydrologic cycle can then be defined as hydrology (Ackermann et al.,
1955). This definition adds to the arrays of definitions used to describe
hydrology. This circulation takes different forms and at different
conditions. As water circulates round, and being a universal solvent it
allows foreign bodies (salts, organic and inorganic materials and
Pathogens) to mix with it and because of this, the qualities and quantity
of water in circulation at every given time during such circulation
becomes included in the definition of hydrology as we saw in order
definitions.
Historically, hydrology has been a subject of investigation and
engineering for millennia. For example, about 4000BC, the Nile was
dammed to improve agricultural productivity of previously barren lands.
Mesopotamian towns were protected from flooding with high earthen
walls. Aqueducts were built by the Greeks and Ancient Romans while
the history of China shows they built irrigation and flood control works.
The ancient Sinhalese used hydrology to build complex irrigation works
in Sri Lanka, also known for invention of the valve pit which allowed
construction of large reservoirs and canals which still function. In
Nigeria, Kainji Dam built for hydro electricity is equally used for
irrigation farming.
Marcus Vitruvius in the first century B.C. described a philosophical
theory of the hydrologic cycle in which precipitation falling in the
mountains infiltrated the earth’s surface and led to streams and springs
in the lowlands. With adoption of a more scientific approach, Leonardo
da Vinci and Bernard Palissy independently reached an accurate
representation of the hydrologic cycle. It was not until that 17th
century
that hydrologic variables began to be quantified.
Pioneers of the modern science of hydrology include Pierre Perrault,
Edme Marriotte and Edmund Halley. By measuring rainfall, runoff and
drainage area, Perrault showed that rainfall was sufficient to account for
flow of the Seine. Marriotte combined velocity and river cross-section
measurements to obtain discharge, again in the Seine. Halley showed
that the evaporation from the Mediterranean Sea was sufficient to
account for the outflow of rivers flowing into the sea. The 19th
century
saw development in groundwater hydrology, including Darcy’s law, the
Dupuit-Thiem well and Hagen-Poiseuille’s capillary flow equation.
Rational analyses began to replace empiricism in the 20th
century, while
governmental agencies began their own hydrological research
programmes. Of particular importance were Leroy Sherman’s unit
hydrograph, the infiltration theory of Robert E Horton, and C.V. Theis’s
Aquifer test/equation describing well hydraulics.
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Since the 1950s hydrology has been approached with a more theoretical
basis than in the past, facilitated by advances in the physical
understanding of hydrological processes and by the advent of computers
and especially geographic information system (GIS).
According to Singh (2000), the study of hydrology originated in the
design of hydraulic works. This historical underpinning continues to
dominate the scope and the range of hydrologic investigations. It is
therefore no surprise that most often civil engineering is the home of
hydrology. With the changing environmental landscape, however, there
are signs of hydrology becoming a geophysical science in its own right.
3.2 Classifications/Branches of Hydrology
Hydrology has got so many classification and branches with each brand
almost deviating from the other in one form or the other to desire a
different name.
It is instructive to peruse the various classifications of hydrology (Singh,
1993). By definition hydrology can be classified as:
physical hydrology, chemical hydrology or biological hydrology
water quantity hydrology or water quality hydrology
surface water hydrology or subsurface hydrology.
Depending on the type of watershed for which the study of water is
undertaken, it can be classified as: agricultural hydrology, forest
hydrology, urban hydrology, mountainous hydrology, desert hydrology,
wet land hydrology or coastal hydrology.
Considering the form of water or where water occurs predominantly,
this study can be classified as: snow hydrology, ice and glacier
hydrology, atmospheric hydrology or lake hydrology.
Depending on the particular emphasis on land phase or channel phase, it
can be classified as: watershed hydrology or river hydrology.
Hydrology is also classified based on the tool employed for
investigation of hydrologic systems, thus we have: parametric
hydrology, theoretical hydrology, mathematical hydrology, statistical
hydrology, probabilistic hydrology, stochastic hydrology, systems
hydrology and digital hydrology.
The various classifications of hydrology are useful in that they point to
its cope and the range of techniques employed in its study.
110
Branches of Hydrology
As sourced from Wikipedia, the free encyclopedia, hydrology has
branches listed below with their brief explanations.
i. Chemical hydrology is the study of the chemical characteristics
of water.
ii. Eco-hydrology is the study of interactions between organisms
and the hydrologic cycle.
iii. Hydrogeology is the study of the presence and movement of
ground water.
iv. Hydro informatics is the adaptation of information technology to
hydrology and water resources applications.
v. Hydrometeorology is the study of the transfer of water and
energy between land and water body surfaces and the lower
atmosphere.
vi. Isotope hydrology is the study of the isotopic signature of water.
vii. Surface hydrology is the study of hydrologic processes that
operate at or near Earth’s surface.
viii. Drainage basin management covers water-storage, in the form of
reservoirs, and flood protection.
ix. Water quality includes the chemistry of water in rivers and lakes,
both of pollutants and natural solutes.
x. Oceanography is the more general study of water in the oceans
and estuaries.
xi. Meteorology is the more general study of the atmosphere and of
weather, including precipitation as snow and rainfall.
xii. Limnology is the study of lakes. It covers the biological,
chemical, physical, geological and other attributes of all inland
water (running and standing waters, fresh and saline, natural and
manmade).
SELF-ASSESSMENT EXERCISE
List the classifications and branches of hydrology.
3.3 Application of Hydrology
There is no denying the fact that hydrology has got a variety of
applications, hence the study is important. Below are some of the ways
through which hydrological studies are applied:
determining the water balance of a region
determining the agricultural water balance
designing riparian restoration projects
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mitigating and predicting flood, landslide and draught risk
real-time flood forecasting and flood warming
designing irrigation schemes and managing agricultural
productivity
part of the hazard module in catastrophe modeling
providing drinking water
designing dams for water supply or hydroelectric power
generation
designing bridges
designing sewers and urban drainage system
analysing the impacts of antecedent moisture on sanitary sewer
systems
predicting geomorphologic changes, such as erosion, or
sedimentation
assessing the impact of natural and anthropogenic environmental
change on water resources
assessing contaminants, transport risks and establishing
environmental policy guidelines.
SELF-ASSESSMENT EXERCISE
Increase the number of the applications of hydrology to humanity to Z.
Explain some of the above applications.
3.3.1 Application of Hydrological Knowledge in Nigeria
Nigeria is considered to be abundantly blessed with water resources.
The country is divided into eight hydrological areas and drained mainly
by the River Niger and River Benue and their numerous minor
tributaries as well as by the Lake Chad and the Oguta Lake and the
rivers that discharge into them. There are several other perennial rivers,
example, the Gongola, Hadejia-Jama’ are, Kaduna, Zamfara and Yobe
in the north and the Ogun, Osun, Imo, Cross and Anambra Rivers in the
south (Goldface-Irokalibe, 2005).
According to Iloeje (1972), the eight hydrological zones include:
i. Lake Chad Basin
ii. Sokoto Basin
iii. Hadeija Yobe Basin
iv. Rivers Nigeria and Benue Basin
v. Anambra Basin
vi. Imo-Akwa-Ibom, Cross River Basin.
vii. Ogun-Osun- Osse Basin
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viii. Delta Basin.
Nigerian hydrological blessings are maximally used as we have hydro-
electricity generated from it as seen in Kainji Dam. We equally have
irrigation made possible in the same damming of River Niger.
Furthermore, there are other uses such as in lumbering and
transportation.
4.0 CONCLUSION
From our discussion we can make bold to conclude that hydrology has a
variety of classification and branches, all which help in designating the
discreet fields or areas into their scope and range of techniques used in
studying them. Because of its wide range of applications and its
ubiquitous nature, man has since creation been studying it even without
knowing. Nigeria as a nation cannot deny having benefited from
hydrological studies.
5.0 SUMMARY
In this unit, you have learnt the meaning and historical background of
hydrology.
You also learnt that hydrology has a vast range of classification and
branches all of which help in dealing with and understanding of the
same. Examples of such classifications and branches include; physical
hydrology, surface water hydrology, agricultural hydrology and
chemical hydrology, hydrogeology, surface hydrology respectively to
mention but a few.
The classifications/branches give a wide view of its applicability; hence
so many professionals are involved in the study of hydrology in one
form or the other.
Its uses are found in agriculture, electricity generation, and designing
bridges etc. Nigeria too has benefitted much from the study of
hydrology.
6.0 TUTOR-MARKED ASSIGNMENT
1. Mention the classifications of hydrology.
2. List its varied applications.
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7.0 REFERENCES/FURTHER READING
Ackermann, U. C, Coleman, E.A, & Ogrosky, H.O. (1955). ‘From
Ocean to Sky to Land to Ocean.” U.S Department of Agriculture
Yearbook, pp. 41-51. Washington, D.C.
“Centre for Ecology of Hydrology Home”.
Goldface-Irokalibe (2005). Water Management in Federal and Federal-
Type Countries: Nigerian Perspective. Zaria: Ahmadu Bello
University Press.
Iloeje, N. P. (1972). A New Geography of Nigeria. Ikeja: Longman
“International Water Management Institute (IWMI) Home
Page”.Iwmi.cgiar.org.http//www.iwmi.cgiar.org/ Retrieved 2012-
02-15.
Murugesu, S. (2005). “Patten, Process and Function: Elements of a
Unified Theory of Hydrology at the Catchment Scale.” In: M. G.
Anderson (Ed.). Encyclopedia of Hydrological Sciences.
Australia: John Wiley & Sons Ltd.
Natural Weather Service. Office of Hydrologic Development Weather-
gov.2011-10-28. http://www.weather.gov/ohd/ Retrieved 2012-
02-15.
Singh, V. P. (2000). Hydrology:The Engineering Book. Boka Raton:
CRC Press LLC.
Singh, V. P. (1993). Elementary Hydrology. Englewood Cliffs, NJ:
Prentice Hall.
“USGS Water Resources of the United States”. Water. usgs.gov 2011-
10-04 http//water.usgs.gov/ Retrieved 2012-02-15.
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UNIT 3 HYDROLOGICAL CYCLE
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Hydrological Cycle
3.2 Effect of Climate Change on Hydrologic Cycle and Water
Resources
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/ Further Reading
1.0 INTRODUCTION
Having been fully introduced into this course in the two previous units,
the onus lies on us now to discuss what is called hydrological cycle. The
world ‘cycle’ connotes a roundabout movement which starts from one
end and comes back to its starting points in a circular manner. A closer
look at it shows that the starting point may be difficult to locate.
Bringing in this cyclic movement into hydrological studies informs what
we may call hydrological cycle.
By design or accident, nature has come in to impact on the cycle of
water (hydrological cycle) at a rate that a conscious man need to watch
with expectancy. This unit is poised to look into water cycle and the
influence or effect of climate change on hydrologic cycle and water
resources. Be comfortable as you read down the lines.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
describe and make a diagrammatic sketch of the hydrological
cycle
explain the effect of climate change on hydrological cycle and
water resources.
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3.0 MAIN CONTENT
3.1 Hydrological Cycle
By way of definition hydrologic cycle is the cyclic transfer of water
vapour from the earth’s surface through evapo-transpiration into the
atmosphere, from the atmosphere through precipitation back to earth and
through runoff into streams, rivers and lakes and ultimately into the
oceans, and the cycle starts all over again.
The central theme of hydrology is that water circulates throughout the
earth through different pathways and at different rates. The most vivid
image of this is in the evaporation of water from the ocean; which forms
clouds. These clouds drift over the land and produce rain. The rain water
flows into lakes, rivers or aquifers. The water in lakes, rivers and
aquifers then either evaporates back to the atmosphere or eventually
flows back to the ocean, completing a cycle. Water changes its state of
being several times throughout this cycle. By changing state of being we
mean changing from liquid to gaseous, from gaseous to liquid and from
solid to gaseous or liquid as the case may be. Can you guess when these
happen in water? Have you ever seen ice block turn into liquid or gas?
Can you give the names of these phenomena? If no, try and find them
for a clearer understanding or you may read on as you will see terms
like: evaporation, sublimation and condensation before the day ends.
The Cycle’s Diagrammatic Presentations
Atmosphere
INPUT: Magmatic Wat
Evaporation
SEA
Surface
run off Precipitation
On land
Ground water Flow
Flow
Transpiration from
plant
Evaporation
from soil
Infiltration
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Fig.3.2: Hydrological Cycle
Source: US Global Change Research Program,
http://www.usgcrp.gov/usgcrp/program element/water.htm
The sun drives the hydrologic cycle, whereby water is evaporated by
solar radiation from oceans, inland water bodies and soil, condenses and
falls on land as precipitation, and returns to receiving water bodies by
either surface- runoff or ground water discharge. Water can enter the
atmosphere from magmatic water during volcanic eruption.
There are many critical sub-cycles within the overall hydrologic cycle.
For example a portion of precipitation is returned to the atmosphere by
evaporation before it reaches the ground. A portion of precipitation that
is stored on vegetation (interception storage), on the land surface in
puddles (depression storage) or in shallow soil pores, also evaporates
rather than moving downward to groundwater (percolation) or running
off to surface water channels.
Precipitation infiltrating the soil that is not lost to evaporation can flow
downward to recharge ground water, contributing to a rise in the water
table, or flow shallowly in a lateral direction and discharge to streams.
Flow in streams that is not due to surface or shallow subsurface runoff
from the land is termed base flow, and such base flow in natural systems
Fig 2
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arises from deep and shallow ground water discharging the streams
during both storm and non-storm periods.
From all the above and according to the U.S Geological Survey (USGS),
there are 16 identifiable components of the hydrological cycle. They are
as follows:
water storage in oceans
evaporation
sublimation
evapo-transpiration
water in the atmosphere
condensation
precipitation
water storage in ice and snow
snowmelt runoff to streams
surface runoff
stream flow
freshwater storage
infiltration
groundwater storage
groundwater discharge
springs.
For a clearer understanding of some of the above terms, some
explanations or definitions are presented below.
Sublimation: It is often used to describe the process of snow
and ice changing into water vapour without first melting into
water. It is a common way for snow to disappear in certain
climates, example in temperate and polar zone.
Evapo-transpiration: This is the process by which water vapour
is discharged to the atmosphere as a result of evaporation from
the soil and transpiration by plants.
Condensation: Condensation is the process in which water
vapour in the air is changed into liquid water. It is crucial in the
water cycle because it is responsible for the formation of clouds.
Precipitation: The clouds so formed above do produce
precipitation which is the primary route for water to return to the
earth’s surface. This is the discharge of water, in liquid or solid
state (ice), out of atmosphere, generally upon a land or water
surface.
Water storage in ice and snow: Fresh water stored in frozen
form, generally in glaciers, ice fields and snowfields.
118
Snowmelt runoff to streams: The movement of water as surface
runoff from snow and ice to surface water.
Surface runoff: Precipitation runoff which travels over the soil
surface to the nearest stream channel.
Stream flow: The movement of water in a natural channel, such
as a river.
Freshwater storage: Freshwater existing on the earth’s surface.
These include streams, rivers, ponds, lakes, reservoir and
freshwater wetlands. Here evaporation can readily occur.
Infiltration: The downward movement of water from the land
surface into soil or porous rock.
Groundwater storage: Water existing for long period below the
earth’s surface. Most of the water in the ground comes from
precipitation that infiltrates downward from the land surface.
Groundwater discharge: The movement of water out of the
ground.
Spring: Place where a concentrated discharge of ground water
flows at the ground surface.
3.2 Effect of Climate Change on Hydrologic Cycle and
Water Resources
1. There are apparent trends in stream flow volume as both
increases and decreases in many regions. These trends cannot all
be definitely attributed to changes in regional temperature or
precipitation. However, widespread accelerated glacier retreat
and shifts in stream flow timing in many areas from spring to
winter are more likely to be associated with climate change.
2. The effect of climate change on stream flow and groundwater
recharge varies regionally and between scenarios largely
following projected changes in precipitation. In some parts of the
world, the direction of change is consistent between the
scenarios, although the magnitude is not. In other parts of the
world, the direction of change is uncertain.
3. Peak stream flow is likely to move from spring to winter in many
areas where snowfall currently is an important component of the
water balance.
4. Glacier retreat is likely to continue and many small glaciers may
disappear.
5. Water quality is likely to be degraded by higher water
temperature, but this may be offset regionally by increased flows.
Lower flows will enhance degradation of water quality.
6. Flood magnitude and frequency are likely to increase in most
regions and low flows are likely to decrease in many region.
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7. Demand for water generally is increasing as a result of population
growth and economic development, but it is falling in some
countries. Climate change is unlikely to have a large effect on
municipal and industrial demands but may substantially affect
irrigation withdrawals.
8. The impact of climate change on water resources depends not on
changes in the volume, timing, and quality of stream flow and
recharge but also on system characteristics, changing pressures
on the system, how the management of the system evolves and
what adaptations to climate change are implemented.
9. Unmanaged systems are likely to be most vulnerable to climate
change.
10. Climate change challenges existing water resources management
practices by adding additional uncertainty. Integrated water
resource management will enhance the potential for adaptation to
change.
4.0 CONCLUSION
From all the forgoing, we can without doubt conclude that hydrological
cycle is cyclic and within the cycle, there are sub cycles. In this
hydrological cycle the sun is the driving force causing evapo-
transpiration from the oceans, water bodies, ground, plants and animals
and when this happens enough, there is the cloud formation which
condenses and falls back as precipitations which enter the oceans, the
ground and the soil eventually and the cycle starts all over again. At
present, there are some noticeable signs of climate change and this
climate change has great effects on the hydrological cycle and water
resource management.
5.0 SUMMARY
In this unit, you learned about the definition of hydrological cycle and
the processes through which the cycle was achieved e.g. evapo-
transpiration, precipitation, sublimation, and infiltration.
Sketches of the processes were given and explanation given to them.
Some identifiable components of hydrological cycles were itemised and
brief explanations given to them.
There were equally some identifiable ways by which the climate change
has affected hydrological cycles. For instance peak stream flow is likely
to move from spring to winter in many areas where snowfall currently is
an important component of the water balance. Equally glacier retreat is
likely to continue and many small glaciers may disappear.
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6.0 TUTOR-MARKED ASSIGNMENT
1. Using an annotated diagram explain in detail the hydrological
cycle.
2. List and explain some ways through which climate change has
affected the hydrological cycle.
7.0 REFERENCES/ FURTHER READING
Arnel, l. N. & Liu, C. (n.d.) Hydrology and Water Resources.
Author, G. & Anne, C. G. (1979). A New Health Science for Africa.
London: Longman Group Limited.
Blyth, F.G.H. & de Freitas, M. H. (1984). A Geology for Engineers.
London: Arnold International Publishers.
Clarie, W. (n,d.). The Urban Water Budget.
Htt://flakes.org/book/water.ENU.CITY/fultext(16).pdf.
Emerson, C.H, Welty, C. & Traver, R. G. (2005). “A Water-shed-scale
Evaluation of a System of Storm Water Detention Basin.”
Journal of Hydrologic Engineering 10 (3), 237-242.
Singh, P. & Keimar, N. (1997). “Impact Assessment of Climate Change
on the Hydrological Response of a Snow and Glacier Melt
Runoff-Dominated Himalayan River.” Journal of Hydrology,
193, 316-350.
The U.S Geological Survey (USGS).
http://us.mg4.mail.yahoo.com/dc/blan.html?bn-
240.3p.intl=usp.lan
US Global Change Research Programme.
http://www.usgcrp.gov/usgcrp/programmeElement/water.htm.
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UNIT 4 ENVIRONMENTAL PROBLEMS OF
URBANISATION AND NATURAL CYCLE OF
WATER
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Meaning of Urbanisation and Characteristics of an Urban
Area
3.2 Urban Water Budget
3.3 Impact of Urbanisation on the Natural Cycle of Water
3.4 Environmental Problems Associated with Urbanisation
and Natural Cycle of Water
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/Further Reading
1.0 INTRODUCTION
Urbanisation which can be described as the increase in the proportion of
people living in towns and cities occurs because people move from rural
areas to urban areas. Such increase makes much demand on land and
water use and occurs at a rate which sometimes poses environmental
problems. In a related manner, urbanisation affects to a great extent the
water cycle in many ways. This altered natural cycle most often poses
environmental problems so much so that man is affected and thus
worried. To deal with this course (Hydrology and Sanitation) well,
proper knowledge of all these phenomena is therefore compulsory.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
define urbanisation and discuss the characteristics of urban cities
discuss urban water budget
explain the impact of urbanisation on water cycle
list and explain environmental problems associated with
urbanisation and natural cycle of water.
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3.0 MAIN CONTENT
3.1 Meaning of Urbanisation and the Characteristics of
Urban Areas
Urbanisation is the increase in number of urban inhabitants as well as
the outward expansion of the urban area. As pointed out in the
introductory note, it occurs because people move from rural areas to
urban areas. It can be described in terms of increasing share of the
national population, activities, properties, and infrastructure and
community services.
Characteristics of urban areas
i. Increased population: Because of the increased upsurge of
people moving to the town and cities for better condition of
living and employment pursuit, people from different
communities with different social, cultural, religions, educational,
economic and ethnic background meet and fill up the towns and
cities. They therefore are heterogeneous in nature in all the above
and the density of the population are always on the increase and
at times get above optimum density.
ii. Changes in land and building use: The wide gap between
population increase and land area or mass, which is fixed, brings
in very serious demands for land, building, road construction,
underground piping of some facilities, establishment of
industries, sporting activities, subsistent and commercial
agricultural production etc.
The effect is that the only option left is expansion, which is encroaching
or extending sub-urban areas, for those towns that still have
undeveloped neighborhood.
Due to social and economic stratification that exist within the urban
areas, the richer ones select those areas that are planned and well
arranged which are normally far from the central business district (CBD)
while the poor ones live in concentrated areas which normally are the
urban slums, blights or ghettos with nothing but struggle for space, air,
food, comfort (privacy) and disease spread.
While a lot of road networks exist, there is few or no tree there in the
urban areas. What exists instead is public and institutional buildings-
banks, sports centres, churches, big markets etc. Also some urban areas
exist around water bodies, examples, Lokoja, a situation which makes it
impossible not to construct bridges across such rivers. Furthermore,
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some towns or urban areas occur because of some mineral deposits
found in or near them making it impossible not to tamper with the sub-
soil for the harnessing of such deposits, examples, Enugu and her coal
deposits, Jos and her tin deposits etc.
All these are in sharp contract with the rural areas where there is no
much interaction or interference with nature - trees (vegetation) are there
not tampered with just as their soil and water. If there are houses, farm
lands and animals etc. they are few.
SELF- ASSESSMENT EXERCISE
What are the effects of urbanisation on water cycle?
3.2 Urban Water Budget
By way of definition “water budget” describes the stores or volumes of
water in the surface, subsurface and atmospheric compartments of the
environment over a chosen increment of time. From the above
definition, one can say that water budget talks about the quantity or
volume of water in a given place or area of interest which can be within
the surface or subsurface over a given point in time.
This quantity or volume gathered is termed its storage value and having
thus gathered, it tends to flow or enter into the next cyclic stage of the
water cycle. Thus the water cycle has to do with characterising the flow
paths and flow rates of water from one store to another. Before water
flows into the next stage or place it must have sufficiently had enough in
its store for there to be a pull. Take for instance, for transpiration to
occur, enough water molecules must have gathered at the stomata of the
leaves so that the excess escapes via the opening and into the
atmosphere. For water to percolate into the deep soil; the top soil must
have had enough in its store, for water to fall back as rain, there must
have been enough in its store (cloud formation) which then condenses
and falls back as rain etc. Having understood the above in words, giving
you this mathematical representation may be of help in making it
clearer.
A water budget or water mass balance can be calculated for any time
increment for a chosen control volume where.
In-flows – Outflows = storage.
Explaining the above, “inflow” is the incoming water molecules while
the outflow is the outgoing where the difference is the storage, and the
124
symbol pronounced delta means ‘change or rate of change in value
of a named quantity.
Some other concepts in water cycle have their mathematical
representations of their storage values, examples:
Precipitation – Runoff - Net Ground water Outflow – Evapo-
transpiration = Storage.
Where the net groundwater outflows is groundwater inflow minus
outflow, and all terms are measured in volumes over the time period of
interest. The change ( ) pronounced “delta” in storage includes
changes in both the amount of water stored in groundwater (or aquifer
storage) as well as in surface reservoirs.
The movement pull in water cycle is controlled by this storage value, i.e.
storage. In a natural setting is in an undeveloped area where there
may not be roads (tarred or un-tarred), houses etc. the rate at which
surface water gathers differs compared with developed area, for instance
in a tarred road where percolation may be difficult. In the latter
situation, evaporation will be faster than the former where for instance
there was none to evaporate since all have entered into the subsoil
(assuming we are considering evaporation only).
Take a look at the subheading above. We are discussing urban water
budget. So far we have only highlighted the phrase “water budget” but
we have almost finished. The last paragraph before this did the magic.
This is because it talked about the rate of generation of storage water in
an urban area where so many activities and infrastructures are in place
and thus disturb the natural setting. Using the specific example in that
paragraph, one will find out that in urban area there are so many road
network everywhere with the result that each time it rains, surface water
emanating from such roads soon accumulate and yearn for their either
drainage (percolation) underground or evaporation into the atmosphere
for another round of rain formation
3.3 Impact of Urbanisation on the Natural Cycle of Water
It is an undeniable fact that urbanisation has some impact on the natural
cycle of water as can be deciphered from the previous section. The
diagram below and the explanations that follow will give you a clear
idea about the impact of urbanisation on water cycle. In urban area, trees
must have been cleared and their place replaced with many buildings or
roads and some open areas have their floors tiled. In some industrialised
areas, big buildings which emit gases of different composition are there,
the same building cover a wide area of space shifting the raindrop of
such spaces. In order to erect some tall building or mount some
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125
machines and sewers found in urban areas, the soil must have been dug
deep to almost reach the impervious zone (e.g. in well construction). In
some areas the presence of water body initiated settlement in the first
instance and such places later turn into urban areas, in that with time,
struggle for spaces occurs and they will shift the water course by
reclaiming some of the continental shelf (near surface areas) with the
result that the water may change its course by force, a situation which
causes harm when river over flows its bank during rainy season.
Construction of dams for irrigation or generation of electricity too also
affects the water volume and course, pipes buried underground too
which may be for portable water supply, storm water, waste water,
petroleum products etc. all destroy the soil composition and affect the
generation of our storage water which creates the enabling potentials
gradient for the water cycle at a given point in time.
The summary of all the above is that the course or flow pattern of water
in its cyclic form is severely affected in urban area when compared with
the naturally underdeveloped or undisturbed area. Such change of course
is shown in Figure 4.1 below.
Fig.4.1: The Urban Water Cycle
126
Fig.4.2
Fig. 4.3
From the diagram, you can see how drastically the density and
connectivity of the flow channels have been altered due to construction
of buildings and roads. In some location, on this map it is difficult to
discern the direction of surface water flow, owing to the high degree of
landscape alteration. The vast network of pipes and utility conduits
underlying urban areas can also significantly affect the cycling of water.
This effect is much more difficult to quantify because the systems are
hidden.
Model result for pre-development
surface water flow (solid line),
Post-development flow (dash-dot
line)
And post development flow (with
detention (dashed line) for storm
having a duration of 6 hours and
return period of two years, applied to
a 6 acre site from Valley Creek water
shade, Pennsylvania (©Emerson,
2003
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The figure above is a conceptual cross-section through the surface and
subsurface where blue arrows depict a position of the natural system
flow paths and the red arrows shows how the built environment alters
the route that water takes.
The effects of urbanisation on the water cycle include:
short – circuiting or path – lengthening compared to the natural
system
leaking pressurised water distribution systems can contribute to
groundwater recharge
cracks in parking lots and other sealed surfaces can act as focused
recharge point to the subsurface (Sharp et al., 2006)
joints and cracks in sanitary and storm servers can serve as drains
for groundwater; conversely these pipes can also leak to
groundwater, causing water quality impairment
utility conduits and tunnels themselves can act as preferential
flow channels for groundwater drastically altering the effective
permeability of the subsurface (sharp et al., 2003)
treated waste water discharge into a stream supplements base
flow and in some cases
accounts for the greatest portion of stream flow
human enhance the conditions for flood production in cities by
hardening the land surface
and by tiling floor spaces of the eternal compound , parking lots,
road construction ( tarred roads)
impervious areas, compacted soils and built up spaces cause
storm water to run off
instead of seeping into the ground and the highly engineered
storm dram system carries
water quickly away from properties .
SELF-ASSESSMENT EXERCISE
i. Check out any mechanic workshop and after rainfall use your hoe
and dig the ground, do same to an unused place (no building,
road or other thing), find out the thickness (depth) of water
penetration in both of them. Or check out the rate of generation of
surface run off. Which one is thicker (depth wise) or faster (for
surface run off).
ii. Make a labeled sketch of your own and show flow rate of water
of a town nearest to you explain the diagram.
128
3.3 Environmental Problems Associated with Urbanisation
and Natural Cycle of Water
a. Urban storm water generation: Because of the reduced rate of
penetration, water runoff soon accumulate and settle on surface
any where is a depression and they are not scarce due to heavy
traffic. The result is that mosquitoes and other flies breed there
and fecal matters too accumulate and serve as a point of
collection for housefly and other vectors. Some helminthes too
complete their cycle in such places where streams may be far.
Such water provides moisture needed for decay of solid refuse
which in turn reduces the ponds storage gradient potential so that
evaporation and or percolation may be hampered. Under this
condition before any of the above occurs, odour nuisance and the
likelihood of disease spread might have been affected.
b. Pollution of underground water source like shallow springs and
wells can be higher in urban areas due to leakage through the
joints and cracks in sanitary and storm water pipes
(see impact (iv) above).
c. Treated and or untreated wastewater discharge into streams and
rivers faster in urban area. When this is done, pollution of such
water is effected which poses problems with the result that
aquatic life may be adversely affected or the quality of water for
some uses may become severed.
d. Where there has been interference with water bodies like streams,
rivers or oceans by undue reclamation of any position of same
due to city expansion, most often such places become submerged
with its negative consequences on the life and property of man.
e. Damming of rivers for electricity and or navigation which creates
more surfaces of water for evaporation causes displacement of
people from their natural or ancestral homes. For example, during
the construction of Kainji Dam, earlier settlers were relocated or
resettled at New-Bussa. At present due to quest for irrigation
farming, enjoyment of electricity and easier sea transportation, all
these can initiate urbanisation there which may later pose a
problem as stated in (d) above.
f. Such interference with the water courses and the undue tempering
with the sub soil due to urbanisation at the upper course of the
rivers cause the formation of heavy depositional features at the
lowest course, example in the delta region with the result that
estuaries spring up more in such place making navigation
impossible at the middle and lower course. That is why Nigeria is
spending heavily now in an effort to dredge rivers Niger and
Benue.
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4.0 CONCLUSION
In the light of all the foregoing, we can conclude that urbanisation has
effects on hydrological (water) cycle. Such effects can be positive (when
it speeds up a given local cycle) or negative (when it protracts a given
local cycle). In most of the above it has or creates some serious
environmental health problems as we have seen above.
5.0 SUMMARY
In this unit, you have studied the meaning of urbanisation. You also
learned that urban areas have a lot of inhabitants who are heterogeneous
in everything and numerous activities take place there just as numerous
buildings are found there.
Water cycle in urban areas is governed by the nature of water budget
found there and these are dependent on the nature of built up
environment as the built up environment creates enough storage
potential gradient to shift the flow to another level which is faster than
the un-built areas.
There are enough pronounced impacts of urbanisation on the water cycle
as has or can be seen above. Thus we have issues like; short-circuiting
or part lengthening, when compared to natural system and leaking
pressurised water system contributing to groundwater recharge. Some or
most of these impacts have serious environmental health problems and
some of the impacts too impact negatively on the cycle itself.
6.0 TUTOR-MARKED ASSIGNMENT
1. Define water budget.
2. List various ways through which urbanisation affects water cycle.
3. Enumerate environmental problems associated with urbanisation
and natural cycle of water.
7.0 REFERENCES /FURTHER READING
Berbery, E. H. (2002). “The Hydrologic Cycle of the La Plata Basin in
South America.” Journal of Hydrometeorology 3, No. 6 p 630-
645.
Claire, W. (n.d.). The Urban Water Budget. . http:// flakes. Org/ book/
WATER-ENV-CITY/fult ext (16) .pdf. Retrieved 15 /06 /2012.
130
Freedman, B. (1995). Environmental Ecology. (2nd
ed.). San Diego:
Academic Press.
Healy, R. W. et al.. (2007). “Water Budget: Foundation for Effective
Water resources and Environmental Management.” U.S.
Geological Survey Circular. 1308 p.90.
Herschy, R. & Rhodes, F. (Eds). (1998). Encylopedia of Hydrology and
Water Resources. Boston, Kluwer: Academic Publishing.
Iloeje, N. P. (1972). A New Geography of Nigeria . Ikeja: Longman
Nigeria Limited.
Ricklefs. R. E. (1990). Ecology. (3rd
ed.). New York: Freeman.
Sharp, J.M.et al. (2003). “Effect of Urbanisation on Groundwater
System.” In: Earth Science in the City. Washington D.C:
American Geophysical Union.
Sharp, J. M. et al.(2006). “Changing Recharge and Hydrogeology in an
Urbanising Area – Example of Austin, Texas, USA.”
Philadelphia Annual Meeting (22-25 October 2006) Geological
Society of America, Abstracts with Programs, 38(7) 289.
Us Global Change Research Program, http. // www.us
gcr.gov/usgcrp/program elements
/water.htm Retrieved 15 /06 /2012
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UNIT 5 PHYSICAL, CHEMICAL AND BIOLOGICAL
PRINCIPLES OF WASTEWATER
TREATMENT
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Sources and Composition of Wastewater
3.2 Meaning and Stages of Wastewater Treatment and their
Processes
3.2.1 The Physical Principles of Waste Water Treatment
3.2.2 The Biological Principles of Wastewater Treatment
3.2.3 The Chemical Principles of Wastewater Treatment
3.3 Application or Importance of Wastewater Treatment
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References /Further Reading
1.0 INTRODUCTION
Man undeniably uses water for most of his activities. Such uses are not
terminal to water as they only change the qualities and quantities of
water within such periods. He drinks fairly wholesome water and passes
some of it out as urine with urine contents, he washes his clothes or
baths with fairly pure water and throws away the dirty water with its
new composition, he goes to toilet and flushes same with clean water
only for the water to increase in volume and weight with human faeces.
The list is endless. More so, many a time it rains heavily and the runoff
water will add to the yolk of man by gathering the residuals of human
wastes and causing undue pond formation or stagnation of existing
drainages with water that its chemistry will be hard for anyone to know.
If not checked, man will soon be engulfed with such water and reap it
surplus negative fruits.
But God in his infinite mercy and wisdom has given man some finite
wisdom to handle such a situation. This must be in line with the divine
injunction that man should conquer the world. The foregoing informs
the reason for wastewater treatment. It is a conscious effort to help in the
cycle of water with no diseases transferred to man as the cycle
continues. This all important treatment takes the physical, chemical and
biological principles.
132
2.0 OBJECTIVES
At the end of this unit, you should be able to:
state the composition of wastewater
discuss wastewater treatment and the stages involved
explain the physical, chemical and biological principles
involved in the processes wastewater treatment
state the importance or uses of wastewater treatment.
3.0 MAIN CONTENT
3.1 Sources and Composition of Wastewater
Whereas we may say the sources correctly, that of the composition will
only be mentioned on a macroscopic point of view, that is, the major
components without reference to their elemental composition. Generally
the sources of wastewater include:
a) Domestic (wastewater from kitchen, sinks wash hand basin,
bathroom and toilet)
b) Industries
c) Groundwater
d) Meteorological or storm water. (Sridhar, 2007)
e) Laundry.
The composition: For the composition of wastewater, the source
determines the constituents. For instance, domestic wastewater may
contain oil, soap, dirt, debris from kitchen, urine, faeces, dissolved and
suspended solids.
Industrial wastewater contains such things like; various organic and
inorganic compounds, toxic chemicals, water, dirt, etc.
Storm water contains dissolved gases, dissolved minerals (sodium,
potassium chlorine etc.) organic debris, stones, leaves, metals, fibres,
etc.
According to Sridhar (2007), the composition of wastewater, is analysed
using several physical, chemical and biological measurement, and the
most common analysis include the measurements of solids, biochemical
oxygen demand (BOD), chemical oxygen demand (COD) and pH. He
states that solids in the wastewater can be divided into volatile or fixed
solids where the volatile solids are generally organic matter.
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The organic matter in typical domestic sewage is approximately 50
percent carbohydrate, 40 percent protein and 10 percent fat; the pH can
range from 6.5 to 8.0. The composition of industrial waste cannot be
readily characterised by a typical range value because its make-up
depends on the types of manufacturing involved, (Sridhar, 2007). The
concentration of organic matter is measured by the BOD and COD
analysis.
According to him, BOD is the amount of oxygen used over a five-day
period by micro-organisms as they compose the organic matter in
sewage at a temperature of 200 C
(680 F
). The COD is the amount of
oxygen required to oxidize the organic matter by use of dichromate in an
acid solution and to convert it to carbon-dioxide and water. The value of
COD is always higher than that of BOD because many organic
substances can be oxidized chemically but cannot oxidize biologically.
Commonly, BOD is used to test the strength of untreated and treated
municipal and biodegradable industrial wastewaters. COD is used to test
the strength of wastewater that contains compounds that inhibit
activities of microorganisms. The pH analysis is a measure of the acidity
of a wastewater.
3.2 Meaning and Stages of Wastewater Treatment
We can say that wastewater treatment simply means the scientific
method of handling and processing the contents of our used water that
are already polluted and contaminated with a view to making such water
relatively harmless and purer.
Stages involved in doing the above depend on the scale of operation, the
degree of contamination and the intended use of the water after the
treatment. For individual household or small communities, treatment can
be at personal level where the use of septic tank and sock away will
suffice. But in large cities, well developed large scale treatment is
needed.
To effect this large scale treatment, wastewater from families is
connected to the treatment plant. Collection can be through separate or
combined piping. It is separate if there are two pipes, one carrying
domestic wastewater (sewage) and the other carrying the storm water
but it is combined if the two are carried through the same pipe.
The stages are shown in the diagram below.
134
Fig.5.1: Sewage Treatment Plant Source: Okoli (1990)
The stages involved are:
1. Primary stage: Physical process
2. Secondary stage: Biological process
3. Tertiary stage: Chemical process
3.2.1 Primary Treatment (Physical Process)
The sewage enters the collection box and goes for screening which helps
to remove larger solids by passing them through the bar screen. The
larger solids can then be removed.
Another system which can go instead of screen is the use of
communitor. This not only screens but can cut drum which cut softer
solids so as to pass through it. It is slotted drum which cuts solids into
smaller particles and screens hard ones it cannot cut (it rotates in the
sewage and breaks the solid wastes).
After screening, the effluent is passed into the second chamber known as
‘Grit Removal’ which removes the finer suspended matter that could not
be screened. The difference is that it moves with a reduced velocity
Slud
ge
dige
ster
Surplus
activated
sludge Raw
sewage Coll
ectio
n
Box
Scr
een
Grit
Remo
val
Prim
ary
sedim
en
tation
Aeratio
n
filtration
Final sed
ime
ntatio
n
Final effu
lient
Digested
sludge to
drying beds
EHS 304 MODULE 3
135
which settles down the finer substances. However, smaller solid
particles still pass along with the sewage.
The next is sedimentation. It is the main process of primary treatment.
This removes as much as possible the organic matter of sewage. The
sewage is allowed to flow in a rectangular tank. Some of them have
paddles which help to rotate the sewage and collect the heavy particles
(solid organic matter, inorganic matters) together and make them to sink
as sediment. Within the tank, it stays two to eight hours. At the end of
this period, this process removes about 60 percent of suspended solids
and about 40 percent of bio-chemical oxygen demand (BOD). The solid
particles are directed to the sludge digester for treatment and the effluent
to the next apartment called the activated sludge (surplus) or
filtration/aeration chamber.
3.2.2 Secondary Treatment (Biological Process)
This process involves the oxidation of the sewage by aerobic bacteria
that is contained in the sewage. It starts with filtration which is achieved
with biological filters (percolating or tricking filters). They are beds of
broken stones or gravels which the sewage is spread over and it
percolates or seeps in the water and the solids are collected by the
stones. Some bacteria on the stones can now oxidize the water apart
from collecting the solids.
In the same apartment there is a provision for surplus-activated sludge.
Here the sewage is continuously rotating and activated thereby keeping
the content oxidized and ready for final sedimentation.
Final sedimentation
Here the remaining solids settle on top while the effluent goes into a
lake or river, sea or any other place while the surplus-activated sludge
should be collected and re-cycled starting from the primary
sedimentation (rear side of it). It should be directed to the sludge
digester and have the action as anaerobic. The sludge is pumped into
digested anaerobic sludge, dewatered and tarry odour (innocuous). Gas
could be produced (as fuels etc) while the effluent is discharged into the
river. Dewatering means “air drying”.
3.2.3 Tertiary Treatment (Chemical process)
If the receiving body of water requires a higher degree of treatment or if
the final effluent is intended for reuse, tertiary wastewater treatment is
necessary. According to Sridhar (1995), tertiary or third stage treatment
136
is generally used to remove phosphorus. To make the water purely
useful for other things, Sridhar (2007) advocates for even further
advanced wastewater treatment.
But other opinions have it that it is not only phosphorus that is removed.
As sourced from Pipeline Summer, there is the need for disinfection of
the final effluent from the secondary stage. Accordingly, disinfection is
normally the final treatment step for wastewater being discharged near
or directly into surface water or for groundwater recharge. Chlorine,
ozone, ultra-violet light, or other chemical agents inactivate many
pathogens that manage to survive previous treatment processes.
Advanced treatment might include additional steps to improve effluent
quality by removing refractory pollutants (Sridhar, 2007). Processes are
available to remove more than 99 per cent of the suspended solids and
BOD. Dissolved solids are reduced by processes such as reverse
osmosis and electro dialysis. Ammonia stripping, denitrification and
phosphate precipitation can remove nutrients. If the wastewater is to be
reused, disinfection by ozone treatment is considered the most reliable
method other than breakpoint chlorination. Application of these and
other advanced wastewater treatment methods is likely to become
widespread in the future in view of the new effort to conserve water
through reuse.
3.3 Application or Importance of Wastewater Treatment
i. Disease prevention: Wastewater treatment consists of a
combination of processes used to remove, kill or inactivate a
large portion of the pollutants and diseases-causing organisms in
wastewater. In fact, ensuring proper waste water treatment and
disposal is as important for protecting community health as
drinking water treatment, garbage collection, and immunisation.
ii. Untreated wastewater can spread disease and contaminate
drinking water sources. It can equally cause harm to aquatic life.
When untreated wastewater reaches water used for drinking by a
community, there can be significant health risk. The effectiveness
of drinking water treatment can be reduced when water is heavily
contaminated with waste. To ensure safe drinking water,
communities need both effective water and wastewater treatment.
iii. Wastewater treatment ensures that no wastes finally exist. This is
because the sewage sludge can be used as fertilizer (as it contains
nitrogen and phosphorous) or can be used for land reclamation.
iv. It ensures the cyclic return of some substances.
EHS 304 MODULE 3
137
SELF-ASSESSMENT EXERCISE
Highlight other uses or importance of wastewater treatment.
4.0 CONCLUSION
Waste water generation is an everyday occurrence and once generated
needs to be taken care of or it indirectly takes care of the generator
through disease breeding and spreading. There are measures that can be
taken by man which are varied in scale depending on number of people
involved. On a small scale, the soak away can end it but on a larger
scale sewage system comprising of sewage and storm water in sewers
end up in a wastewater treatment plant which uses physical, biological
and chemical processes to achieve its desired results.
5.0 SUMMARY
In this unit, we were able to understand that wastewater is a wonderful
mixture with its constituents that are either organic or inorganic, solids
or liquid in solution, colloidal or suspension as the case may be.
There are three main processes by which the impurities in wastewater
are handled- physical, biological and chemical processes.
The physical process ensures the removal of the solids organic or
inorganic. The biological process ensures that certain impurities or even
pathogens are killed or have their virulence attenuated by the actions of
some aerobic bacteria which oxidize the water. While the chemical
process ensures that a full stop is put to the action of the stubborn
pathogen that might have survived all the processes or the other
chemical pollutants that might have been with the water all these time of
the treatment.
Man does not waste time doing all these in vain. Numerous advantages
go with it as we saw notable among them are disease prevention and the
cyclic return of some substances like water.
6.0 TUTOR-MARKED ASSIGNMENT
1. Using an annotated diagram describe only the physical and
biological process of treating wastewater.
2. Has it any use?
138
7.0 REFERENCES/ FURTHER READING
Ademoroti, C. M. A. & Sridhar, M.K.C. (1979). “Fluidised Bed
Technique Physico-Chemical Treatment.” Effluent and Water
Treatment Journal. U. K.19: 291-297.
Hammer, M. J. (1986). Water and Wastewater Technology. SI Version.
(2nd
ed.). New York: John Wiley and Sons.
Okoli, E. C. D. (1990) ‘Waste Disposal Management.’ Unpublished
Lecture delivered at the School of Health Technology, Oji River,
Enugu State.
Sridhar, M. K. C. (2007). “Sewage Treatment.” Lecture delivered during
the 2007 mandatory Continuous Education Programme (MCEP)
for the Environmental Health Officers Registration Council of
Nigeria, at Filbon Guest House, New Haven, Enugu.
Sridhar, M. K. C. (1995). “Sullage/Wastewater in Nigeria: Problems and
Solutions for Utilisation for Gardening.” A Report submitted to
UNICEF, Lagos, Nigeria.
“Wastewater Treatment Protects Small Community Life Health.”
Pipeline Summer 1996, Vol 7, No. 3.
West Africa Health Examination Board (1991). Waste Disposal and
Environmental Hazard Control. Ibadan: Sterling Publishers Ltd.
EHS 304 MODULE 3
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MODULE 2 WATER SANITATION AND MUNICIPAL
SERVICE
Unit 1 Definition, Concepts, Theories of Sanitation and
Application of Water to Sanitation
Unit 2 Sources of Water and its Protection
Unit 3 Water Sampling Techniques
Unit 4 Water Supply and Distribution
Unit 5 Environmental Problems of Water Supply and Distribution
UNIT 1 DEFINITIONS, CONCEPTS, THEORIES OF
SANITATION AND APPLICATION OF WATER
TO SANITATION
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Definitions of Sanitation
3.2 Concepts of Sanitation
3.3 Theories of Sanitation
3.4 Application of Water to Sanitation
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References /Further Reading
1.0 INTRODUCTION
In module 1 we dealt much with hydrology and its cyclic nature. In this
module we will look into water and sanitation. Whereas water is a
source or an instrument of achieving good sanitation, it needs equally to
be sanitised for yielding effective results, or else, negative consequences
will follow.
In this unit specifically, we are going to deal with definition, concepts
and theories of sanitation and application of water to achieving good
sanitation.
140
2.0 OBJECTIVES
At the end of this unit, you should be able to:
define sanitation
explain some concepts of sanitation
discuss theories of sanitation
discuss applications of water to sanitation.
3.0 MAIN CONTENT
3.1 Definitions of Sanitation
According to Wikipedia, the word “sanitation” is the hygienic means of
promoting health through prevention of human contact with the hazards
of wastes. Hazards can either be physical, microbiological, biological or
chemical agents of diseases. Wastes that can cause health problems are
human and animal faeces, solid wastes, domestic wastewater industrial
wastes and agricultural wastes.
Hygienic means of prevention can be by using engineering solutions
(e.g. sewerage and wastewater treatment), simple technologies (e.g.
latrines, septic tanks) or even by personal hygiene practices (e.g., hand
washing with soap).
World Health Organisation defines sanitation as the provision of
facilities and services for the safe disposal of human urine and faeces.
However, sanitation to us is the taming of our environment so that it can
no longer constitute hazard to man.
Inadequate sanitation is a major cause of diseases worldwide and
improving sanitation is known to have a significant beneficial impact on
health both in households and across communities. The word sanitation
also refers to the maintenance of hygienic conditions through services
such as garbage collection and waste water disposal.
SELF-ASSESSMENT EXERCISE
Give your own definition of sanitation and state its importance.
3.2 Concepts of Sanitation
The term “sanitation” can be applied to a specific, location or concepts.
There are many concepts or ideas under which sanitation can be
discussed. For brevity some of them are summarised below:
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141
(a) Environmental sanitation: This refers to the control of
environmental factors that form links in disease transmission.
Subsets of this category are solid waste management, water and
wastewater treatment, industrial waste treatment and noise and
pollution control. According to WAHEB (1991), problem
connected with the storage, collection and disposal of waste
include unsightliness, insects and helminthes breeding and
transmission of diseases, cat infestation and transmission of
disease like plague and Lassa fever. When properly disposed of
and on time, most of the above will be disposed of. In separate
surveys by Central Public Health Engineering Research Institute
(1993) and WHO Expert Committee (1971) in India, it was
discovered that apart from diseases for which insects and rats are
carriers, the handling of refuse can cause illness to works
especially if night soil contaminates the waste. Other effects of
wastes on health are accidents, atmospheric pollution, and spread
of communicable diseases, especially those of the gastrointestinal
tract, poisoning and exposure to radioactive elements.
(b) Food sanitation: This refers to the hygienic measures for
ensuring food safety. These measures range from the quality of
the raw food items, to the environment where it is prepared and
its preparation methods and techniques. It also includes the food
handlers’ personal hygiene and the quantity and quality of water
used in such preparation.
(c) Ecological sanitation: This refers to the approach that tries to
emulate nature through the recycling of nutrients and water from
human and animal wastes in a hygienically safe manner.
(d) Water sanitation: This is the process of removing all the foreign
substances and protecting the water from pollution or
contamination. Ways of attaining the purity of sanitised water
and the use of water in achieving other aspects of environmental
sanitation form the bulk of the entire work and therefore will be
seen in subsequent units.
(e) On-site sanitation: Under this arrangement, the collection and
treatment of waste is done where it is deposited. Examples are the
use of pit latrines, septic tanks and Imhoff tanks.
There are other concepts or types of sanitation (Lucas and Gilles,
1984; Njoku, 1978; WAHEB, 1991). Some of these are given
below.
(f) Market sanitation: This is the keeping of our markets and their
surroundings satisfactorily clean and safe - health wise. It needs
quality spatial arrangements of the market stalls, adequate
aeration of the entire market, proper collection and disposal of
solid waste, proper drainage of the market places, provision and
use of adequate number of conveniences ( urinary and toilet
142
accommodation) and the sale of wholesome goods and services
in the market. Good sanitation in market improves quality of
human life, reduces death rate and increases life expectancy
(WAHEB, 1991).
(g) School sanitation: This involves the provision of adequate
accommodation for pupils and students, and such spaces
provided having enough ventilation and lighting. Other
requirements include the maintenance of general environmental
cleanliness, provision of functional toilet and urinary
accommodation that are adequate in terms of their number,
provision of adequate and constant supply of water for the use by
the children.
(h) Building sanitation: This aspect of sanitation is concerned with
the qualities of our buildings and the conditions of their
surroundings. In building sanitation we talk about the nature and
arrangement of the building materials. With their ventilation and
lighting being considered most, the use of such spaces to reduce
overcrowding is of necessity. Also included is the checking of
evidence of rodent infestation and the provision of conveniences
and how adequate such provisions are, the condition of the
ceilings, floors and walls. When all these are in order, the life of
the inmates will be prolonged as air borne diseases and others
will be reduced.
(i) Sanitation in abattoirs: Abattoirs or slaughter houses are places
where animals mostly meant for sale for human consumption are
butchered or slaughtered. Because of the importance of these
places to man, proper sanitation is needed. This comes in form of
provision of adequate and functional drainage system, provision
of adequate water supply, proper disposal of bones and animal
wastes (animal dung), provision of supper structures (buildings)
with slab floors for the butchering of animals, provision of
convenience for butchers and the public use, ensuring proper and
constant environmental cleanliness and fly-proof the areas where
the cows are being dismembered to avoid contamination by flies.
When all these are done, food born infections that comes from meat and
meat products will be reduced.
3.3 Sanitation Theories
Just as we have some concepts to explain the scope of sanitation, so we
also have theories of sanitation. Though there are other theories of
sanitation, the most influential of them is that of “Environmental Theory
of Sanitation” by Florence Nightingale. She links good health to clean
and good environmental sanitation and believes that a good sanitation
EHS 304 MODULE 3
143
has a great influence on a person’s health. According to her, there are
five essential elements in healthy home practices and they include:
pure air
pure water
good drainage
cleanliness
light.
She strongly considers that healing would be impossible without proper
order of the environment and without giving the basic needs of the
people.
Therefore, it must be an evident that her theory really deals with the
importance of clean environment and everything that people need in
order to live in a healthy way. For her, clean air and good ventilation are
the best weapons for prevention of any diseases.
Her theory also emphasised that the main cause of any disease is poor
environmental conditions. Therefore to live a healthy life, our
environment must be healthy too.
SELF-ASSESSMENT EXERCISE
Find the other theories of sanitation and comment on them briefly.
3.4 Application of Water to Sanitation
Water is very important to all living things and many activities that
happen in this world. The qualities of water for various uses are not the
same and even the different sources of water do not have the same level
of purity. There is thus the needed level of sanitation required so that all
the blessing derivable from it can be maximised and the evils that may
equally be found in the same substance (water) be minimised.
Whereas the rest of this write up may center on things to be done to
water and other water management strategies, this section is dedicated to
discussing the application of water in ensuring the sanitation of our
environment. Below are some of the applications of water to ensure
sanitation
(a) Flushing and washing our water closets: Irrespective of the
quality of the water, it is used in flushing water closet. For
instance water already used for washing clothes can still be used
in flushing of toilet especially in areas with water scarcity.
144
Relatively cleaner water when mixed with detergent can be used
in scrubbing the floors of the convenience rooms.
At present, conscious effort is being made to ensure that
indiscriminate defecation is totally stooped. Sequel to this, the
federal government through the ministry of health and
environment has come up with a policy aimed at stopping open
defecations tagged “open defecation free” (ODF) which must be
community oriented and community led. Thus we have the new
slogan- ‘community-led total sanitation’ (CLTS).
This new move encourages every member of the community to
participate in community sanitation and encourages individuals to
embrace ODF by making sure that there is provision for toilet
accommodation they can afford that is sanitarily acceptable. This
cannot be achieved without water.
(b) Washing of clothes: Water is used in making sure our clothes
are in good order in terms of cleanliness. Hardness of water
affects this function. To correct this hardness, water needs to be
treated before use for washing. Hardness of water is of two types:
temporary and permanent. Temporary hardness according to
Ebisike et al. (2009) is caused by the presence of hydro
carbonates of calcium and magnesium. This can be removed by
boiling which decomposes the hydro-carbonates precipitating
Ca2+
and Ma2+
ions from the water as the corresponding
carbonates. The equation goes like this:
Ca2+
+2HCO3- →CaCO3 +H2O +CO2.
Permanent hardness which cannot be removed by boiling is due to
dissolved sulphates, chlorides and nitrates of calcium and
magnesium. This one can be treated with a base –exchange resin,
example; sodium zeolite or lime – soda ash or addition of sodium
hexametaphosphate which will render it softened. When treated,
it can effectively be used for washing of clothes etc.
(c) Personnel cleanliness: Without water, achievement of this
cannot be possible. We need water of good quality to wash our
body which removes dirt and helps us achieve good health.
(d) Miscellaneous use: Without water, achievement of adequate
sanitation in our environment cannot be successful. It has a wide
application in achieving sanitation in our homes and our working
environment like in piggery farm, factories, poultry farms, and a
litany of others.
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In fact, apart from provision of certain facilities and amenities, all the
branches, aspects or concepts of sanitation as outlined in this section
need water to become operational and functional, hence the importance
of water to sanitation.
To achieve the above feat however, water itself need to be sanitised in
all ramifications. This calls for water treatment and water quality
control. Treatment can unconsciously start from water sources,
achievable by protecting its sources.
4.0 CONCLUSION
We can conclude this unit by saying that sanitation is an indispensable
phenomenon as achievement of health cannot be successful without it.
Sanitation is involved or employed in many aspects in the course of our
daily life existence. Water is a sine qua non for achieving good
sanitation and it has its own problems if not handle properly.
5.0 SUMMARY
In this unit, you learned about the meaning of sanitation as defined by
many people. Later, concepts or several ideas or branches of sanitation
were given. Similarly, we saw that sanitation has a wide application
such as environmental sanitation, food sanitation, market sanitation and
building sanitation etc.
Also discussed was the theory of sanitation as presented by Florence
Nightingale which links good health with good environmental
sanitation. Finally the application of water to sanitation and the need for
water sanitation to be effectively done before water uses were equally
presented.
6.0 TUTOR-MARKED ASSIGNMENT
1. (a) Define the word sanitation.
(b) Outline seven branches or concepts of sanitation.
(c) Describe theory of sanitation as given by Florence
Nightingale.
2. Without water there will be no sanitation and without sanitation
there will be no quality water supply. Discuss.
7.0 REFERENCES/FURTHER READING
Central Public Health Engineering Research Institute (1973). “Intestinal
Parasites in Refuse.” Technical Digest, No37 Nagpur: CPHERI.
146
Ebisike, A. O. et al. (2009). The Sanitarian and his Work. Ibadan:
Juaaninchrist Printers.
Lucas, A. O. & Gilles, H. M. (1984). A Short Textbook on Preventive
Medicine for the Tropics. London: Hodder and Stoughton.
“Nightingale’s Environmental Theory on Sanitation.”
(http://www.ehow.com/about 6391212 florence- nightingale-
theory. html)
Njoku, A. P. (1978). Certificate Health Science and Health Education.
Onitsha: Africana Educational Publisher, Nigeria.
West Africa Health Examination Board (1991). Water and Building
Sanitation. Ibadan: Sterling Publishers Ltd.
West African Health Examination Board (1991. Waste Disposal and
Environmental Hazard Control. Ibadan: Sterling Publishers Ltd.
WHO and UNICEF. (2012). “Progress on Drinking Water and
Sanitation.” Geneva and New York: WHO.
WHO and UNICEF. (2012). “Types of Improved Drinking Water
Source.” WHO, Geneva and UNICEF, New York, accessed on
June, 10 2012.
WHO Expert Committee (1991). “Solid Waste Disposal and Control.”
Technical Report Series No 484, Geneva: WHO.
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UNIT 2 SOURCES OF WATER AND ITS PROTECTION
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Rainwater
3.2 Surface Water from Streams, Rivers and Lakes
3.3 Sub – Soil or Underground Water from Springs and Wells
3.3.1 Boreholes
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References /Further reading
1.0 INTRODUCTION
Having gone this far, it is pointless to ask if you can correctly guess the
sources of water supply. This is because you know them all. Don’t you?
If you do not, then know it that water can be supplied mainly from rain
water, underground water- wells and springs and surface –dams, lakes,
streams, river, seas etc. The essence of water supply is for use by man,
for all his water needs at home, in industries in his farms and for
animals. The quality of water supplied depends on the source and the
presence of pathogens and other pollutants and containments in such
water. The usefulness of any water supplied depends on the degree of
contamination and the intended purpose or use for which the water is to
be made.
Man, a conscious being needs to do all he can to protect the water, an
unconscious entity which the former uses. Water is a universal solvent
and a free flowing object ready to absorb (dissolve) anything absorbable
and accommodate all that falls within it. Water can therefore be made
harmless to a tolerable extent if we protect it from contamination and
pollution or can be a source of trouble if we do not.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
list the major sources of water
explain how to protect each of these sources from pollution.
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3.0 MAIN CONTENT
The nature and degree of protection due and given to water sources
depend on the source of water itself and the overall intended use of
water to be supplied.
3.1 Rainwater
This is water collected or harvested during rainfall from the surface
using the appropriate instruments.
a. Background: Types of rainfall included: relief or orographic
rainfall, conventional rainfall and cyclonic rain fall (Goh cheng,
1971). Harvesting of rain water is ideal to serve house hold and
small communities. Rain water should be the purest of all sources
but it collects dust, soot, salt and absorbs oxygen and carbon
dioxide from the air. While flowing over the ground, it collects
sediments and particles or organic matter some of which will
ultimately dissolve unit. On inhabited areas, rain comes in
contact with pollutants including faecal matter and pathogenic
organism. Certain wood or paint materials used on roofs and dead
leaves which usually accumulate in the troughs are capable of
imparting taste and colour to water. Rough roof surfaces such as
these made of hatch are likely to retain dust which is later
collected by rain water.
b. Collection: From the above, one can see that rainwater can be
collected using different methods, though some are hygienic,
others are not.
Collecting from zinc roofs, asbestos etc (eaves gutter).
Collecting from the surface of the ground.
Collecting from tree leaves or tree trunk using some
thatches at tree trunks.
Collecting from cultivated areas.
Collecting directly from the atmosphere (WAHEB, 1991).
c. Protection: This forms the mainstay in this discussion.
According to Sarojini (2007), to keep out dust particles, a sieve is
fixed to the funnel through which the rainwater is collected. This
sieve should be periodically cleaned. Water from the tank should
be pumped out through a pipe and not obtained by using a bucket
tied to a rope.
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The collection of rain water requires clean roofs, eave gutters,
collectiontroughs and surface tanks. Galvanised iron, zinc, slate,
aluminum roof all provide excellent and smooth surface for the
collection of rain water (WAHEB).
Rainwater harvesting requires adequate provision for the interception,
collection and storage. To avoid leaves, bird droppings etc from
accumulating on the roof and gutters, the roof should be high pitched,
the gutters should be constructed in such a way that it slopes enough not
to accumulate much volume of water and the pipe should be made to
pour away the first rain outside the cistern (a tank which is made of
metals placed on top or buried underground). Below are some of the
measures given by Nnaji (1990) on how to handle or collect rainwater
and is thus adopted in this discussion.
1. The collecting surface must be clean and impervious, example;
dead leaves, dust, pebbles, and debris must not be in a
collecting surface.
2. The first rain must be run off and discarded especially after a
period of drought. This is in order to get rid of dust, rat urine
and debris etc.
3. The eaves gutter must be designed as to facilitate easy
cleansing, that is it must be slant in positions for all the water to
flow off easily. If not so, it returns water and mosquitoes breed
there.
4. Filters and strainers leading form the mouth of eaves gutter
must be installed and washed periodically. Hence, it must be
moveable, not permanent, sieved, and removable at the end of
rainy season and washed periodically.
5. Lead pipes or lead lines and other lead sea tanks should not be
used for water collection and storage.
6. Storage tank may be located on the surface or underground but
not in an area flooded by running water or near places
contaminated especially to the upper side of the tank.
7. Tanks should be constructed of either concrete, low porosity
bricks or stones with cement mortar. That is, it must be
plastered with cement mortar and allowed to dry and the
interior surface must be rendered waterproof with a well-
trowelled cement plaster and allowed to cure.
8. The tank must have a well fitted mouth hole fitted with cover
and good lock.
9. Water should be drawn from the side, preferably from the lower
part but not on the main bottom. This is to allow some water
remains and with the dirt which can be then washed away
during washing.
150
10. The tank must be screened to keep off or exclude mosquitoesand
other insect.
11. The tanks must be cleansed once in a year and subsequently
disinfected with solutions of chloride of lime which is later
poured off as waste.
For water to be collected directly from the atmosphere, the bucket
should be raised using stool and avoiding any tree, so that no splash
from ground (surface runoff) can get to the bucket.
SELF-ASSESSMENT EXERCISE
Highlight ways through which rainwater can be collected in a safe
manner.
3.2 Surface Water
(a) Background: Water bodies included under this group are the
rivers, ponds, lakes and small upland streams which may
originate from springs. The quality of surface run-off depends to
a large extent on the intensity of rainfall, the climate and
vegetation, geological, geographical and typographical features
of the area. It also depends on the content of living organisms,
amount of mineral and organic matter which it may have picked
up in the course of its flow. The quality of the type of water
bodies under this class differ greatly for the above reason and the
nature of the protection may also vary. Seasonal fluctuations
characterise surface water generally too.
(b) Collection: Collection of this water are done usually with
containers and carried on head, in vehicles or trucks or could be
piped into the cistern depending on its closeness with inhabitants.
The degree of collection depends on populations of consumers,
the purposes for which the water is to be used, climate, type and
nature of industry and level of civilisation.
(c) Protection: Whereas we can, as we have done above give a
general comment on their background and collection, it may not
be possible to give together the protection given to them. This is
because of their varying degree of size, compositions and
closeness to users. To this effect some are taken separately
below.
(i) Rivers and streams
The banks of the rivers should be kept clean.
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Refuse and human and animal waste should not be
dumped into the river.
Water should be drawn from the banks and towards the
centre of river.
Points of discharging pollutants should not be close to one
another.
Water should be drawn upstream of points where washing
is carried out or where animals are watered.
Whenever possible, river intakes should be built upstream
of inhabited communities. The intake should be screened,
submerged and placed below the water surface and not too
close to the river bottom. This prevents any debris or
rolling stone from entering it.
Banks of streams should be trimmed up to a distance of
water 100 metres upstream of the intake.
Farming and animal grazing within this distance should be
prohibited to prevent pollutions.
By constructing jet (a sort of bridge) in the centre to
enable water collection from the centre since its banks are
usually heavily polluted through human activities.
The banks of streams/rivers should be lined with
reinforced concrete and provided with drains to divert run-
offs down-stream drinking points.
Infiltration galleries (horizontal wells) are necessary for
supply of good and wholesome water.
The course of the river should be partitioned with one end
(near the source) as the area for collection of drinking
water, the middle for human use and the end (bottom) for
irrigation and animal grazing. Adopted from WAHEB
(1991).
(ii) Lakes, Ponds, and Storage Reservoirs: Precautions include:
protect watersheds from inflowing streams by constructing
diversion drain which intercept and divert water down-
stream drinking point
prohibit and exclude human habitation, farming, livestock
etc from water shed by fencing it
clear the area of all vegetation and decaying matter
provide de-stilling facilitates for periodic flushing out of
the reservoir adopted from WAHEB (1991).
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3.3 Underground (Sub-Surface) Water Supply
(a) Background: Water bodies under this group include the wells
and spring. This is because they come out form the
subsurface of the earth. This ground water mostly derives
from the portion of rainfall, which percolates into the earth to
form underground deposit. When the percolation (infiltration)
becomes much and when the water reaches impervious layer of
rock, they will well up, raising then, the water table of the area.
When this happens, dug well will allow the out flow of water into
the opening of the well. At times the impervious rock may be
close to the surface and may be rested upon by another layer
(stratum) of hard impervious rock (at the near surface) then
spring water may come out from the aquifer and this serves as the
source of the spring water.
SELF-ASSESSMENT EXERCISE
i. Consult any textbook of yours which dealt on water sources and
make a sketch of a well.
ii. How many types of well do we have?
iii. Distinguish between a well and a spring.
(b) Collection: Irrespective of the type – shadow well, deep well or
artesian well - collection is the same. Collection is done with
buckets with long ropes which are tied firmly at the other end to
the metallic cover or any other strong object, made so in other
that it will not allow the bucket slip into the well.
(c) Protection:
i. In the first place, the well must be constructed at least
100ft (30m) away from any source of pollution or
contaminations, example pit toilet.
ii. The site must be slightly higher than the nearest source of
contamination.
iii. The well should be raised at least 3ft higher above the
ground and the area around it should be concreted and
slightly sloped to allow water flow out.
iv. It should always be covered with a tightly fitting, non
rusty cover and a channel draining water away provided to
avoid contamination.
v. Only one bucket tied accordingly as described above will
be used in collecting water from the well. People should
not use their own buckets.
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vi. The inside of a surface well should be lined with concrete
or bricks at least as far down as the first layer of clay. In a
deep well the liming should extend up to the first non-
porous layer or rock. This prevents the unsafe surface and
subsoil water from mixing with the safe water below the
non-porous layer. Sources WAHEB (1991) and Sarojini
(2007).
Spring water
It is classified under underground water as seen above and its collection
is done by using of containers which are normally put under the piped
source. Springs are broadly classified either as rock spring or earth
spring depending on the source of water. They occur at the out crops of
superficial impervious strata.
Protection of spring
i It should be protected from surface pollution by constructing a
deep diverting drain above and around the spring.
ii It should be encased in concrete or made water tight preferably
with concrete and water obtained by gravity through a discharge
pipe fitted into the collecting basin.
iii A run-off channel should also be provided to take away spillage.
iv A properly installed hand pump will enhance collection of water
on the one hand and also ensure safe potable water to the home.
v People should be discouraged not to have any type of agricultural
activity within a zone of 30m (100ft) around the spring to prevent
pollution through indiscriminate unsanitary human habits.
vi User communities should be encouraged to organize themselves
into a body (village development committee) that should take the
responsibility for the proper operation and maintenance of the
wells and springs.
3.3.1 Boreholes
(A) Background: This is equally from underground source but is
from a very deeper end of it with more complicated methods of
extractions. Boreholes tap underground reservoirs of water. They
are very deep usually going down to a depth of about 100 metres.
Water is usually pumped out by powerful machines at a rate of
about 25,000 litres an hour. The water is stored in a huge tank
usually sited at the highest point in a village or area where such
water is stored. Water from the tank is supplied to people through
pipes- (Sarojini, 2007)
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(B) Collection: Collection is at the taps provided at strategic points
of the area where the boreholes are provided. Tankers,
individuals do the collection for uses by humans.
(C) Protection:
(i) The machines used in pumping out the water should be
adequately cared for. This can be done by ensuring the
greasing of engine parts, maintaining all the systems
and replacing worn out parts as well as adequate fueling
of the machines.
(ii) The pipes should be made with non rusty materials and
with materials that do not dissolve in water.
(iii) The tanks should be regularly checked to avoid leakage
and same should not be open for birds and other flying
insects to pollute or contaminate them.
4.0 CONCLUSION
We have seen all the sources of water and from these we can conclude
by saying that we need to do a lot to make sure that such natural
endowment does not turn against us because of our carelessness. If we
adopt all measures outlined above, disease spread through water will be
a thing of the past.
5.0 SUMMARY
There are mainly four primary sources of water, viz rainwater; surface
water which include streams, rivers, ponds and lake; underground water
which include the wells and spring and finally the bore holes.
Rainwater should have been the purest form of water source but for
impurities that blend with it from the atmosphere. Containers and places
of collection should be cared for to make a fair quality harvest. Surface
water is the most rampant in terms of availability especially where it
exists but they are mostly polluted and contaminated. Protection from
contamination and pollution will help us in reaping from surface water.
Underground water is mostly contaminated when they come out from
the aquifer. Underground contamination can also be possible if our
action near it is unwholesome.
Even the purest form of water through boreholes can be polluted if we
do not protect the containers and the pumping machine.
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6.0 TUTOR-MARKED ASSIGNMENT
1. List all the sources of water supply and explain in details any two
of them.
2. Enumerate ways of protecting any two of the sources.
7.0 REFERENCES/FURTHER READING
Goh, C. L. (1971). Certificate Physical and Human Geography.
London: Oxford University Press.
Nnaji, E. (1990). An unpublished Lecture on “Water Supply and
Sanitation” delivered at School of Health Technology, Oji River,
Enugu State.
Sarojini, T. R. (2007). Modern Biology for Senior Secondary Schools.
Onitsha: Africana First Publishers Ltd.
West Africa Health Examination Board (1991). Water and Building
sanitation. Ibadan: Sterling Publishers Ltd.
156
UNIT 3 WATER SAMPLING TECHNIQUES
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Definition of Water Sampling, the Need for Water
Sampling and Sampling Points
3.1.1 Definition of Water Sampling
3.1.2 Need for Water Sampling
3.1.3 Sampling Point Selection
3.2 Basic Requirements in Collection of Water Sample
3.3 Sampling Procedure and Collection of Samples
3.3.1 Collection from Tap
3.3.2 Collections from Rivers, Stream, Lakes, Springs
3.3.3 Collections from Well Fitted with Hand Pump
3.4 Data Needed During Water Sampling
3.5 Preservation and Storage of Sample
3.6 Cleaning of Glassware Used in Analysis
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/Further Reading
1.0 INTRODUCTION
Having known the sources of water and its needed protection, it is
necessary the quality of such sources be determined before distribution
to the public. The essence of water sampling therefore, is to determine
the level of purity in terms of its physical, chemical and biological
characteristics of any water supplied or intended to be supplied for
human use. As you read along you will see how water sampling is done.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
give the definition of water sampling, explain the need for it and
list sampling points
enumerate the basic requirements in collecting water sample
explain the sampling procedure and the collection of water
sample from different sources
list the data needed during water sampling
explain the preservation and storage of sample
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mention the procedures for cleaning glassware used in analysis.
3.0 MAIN CONTENT
3.1 Definition of Water Sampling, the Need for Water
Sampling and Sampling Points
3.1.1 Definition of Water Sampling
This is the systematic way through which small quantities of water are
collected at different strategic positions of water supplied or intended to
be supplied and taken to laborites for analysis of the qualities.
Samples are just representative form of the entire quantities or volumes
of water from which when analysed can be used to draw conclusion
about the quality of the water being supplied. If the water is
contaminated, the analysis will show the nature of the contaminants and
from which point for action to be taken to remove the contamination.
3.1.2 The Need for Water Sampling
(a) According to WAHEB (1991), the need or reason for water
sampling is to determine the quality of the water that gets to the
user’s tap or other outlets.
(b) Samples are taken from water supply system in order to
determine whether the water supplied is safe for human
consumption. Therefore, there must be a sample of the water
supply (Nnaji, 1990).
(c) Sampling of water is done to prevent waterborne and water-
related diseases from infecting the public.
(d) It is done to determine the extent of treatment that should be
given to a source of water for a particular use.
(e) It is done at strategic points in a water supply system to know
when pollution or contamination started so that intervention can
start from there. This saves time and materials that could be used
for treating the whole water.
3.1.3 Sampling Point Selection
One sample taken from a water system is of limited value, therefore
long records and repeated sampling is desirable. Sampling should be
rotated through all parts of the distribution system. It is probable that the
quality may not be the same as that in the distribution system at the
point where it is connected to a domestic dwelling. In some instance,
158
water may be collected in a storage tank and may be the source of
pollution.
In selecting sample points, each locality should be treated individually.
However, certain general criteria apply to all localities (WAHEB, 1991).
Thus:
sampling points should be selected in such a way that the sample
taken is representative of the different sources from which water
enters the system
these points should include conditions at most unfavourable
places in the system from the view points of contamination,
examples, loops, reservoirs, low pressure zones, end of systems
etc
sampling points should be evenly distributed
sampling points should be located in the open, closed and mixed
distribution system in proportion to the number of links or
branches
sampling points should be chosen such that they are
representative of the system as a whole and its main components
sample points should be located in such a way that water can be
sampled from reserve can and reservoir
in sampling system with more than one water source, the
sampling points should be located so as to take account of the
number of inhabitants served by each source
there should be at least one sampling points directly after the
clean water outlet from each treatment plant.
3.2 Basic Requirement in Collection of Water Sample
Microbiological examination is the main element in the quality control
of drinking water. It entails analysing water samples collected from the
water supply system. Before and during collection of water sample the
following requirements must be met:
sampling should be properly planned and carried out with
sufficient frequency to enable seasonal variation in the quality of
the water to be detected
samples should be collected, stored and distributed in suitable
sterilised bottles
the volume of water collected should be large enough to permit
accurate analysis
the sampling points in the water supply system should be selected
such that the samples collected are representative
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care should be taken to avoid contaminating sample in the
process of collection
samples should be properly collected and dispatched immediately
so as to avoid changes in the composition of the samples
collected
sample bottles should be properly labeled and details accurately
described.
3.3 Sampling Procedure and Collection of Samples
The equipment used for water sample is called “sampling kit.” It is
made up of an insulated box, sterile glass, stopped bottle of about 150-
200 ml in capacity. Below are the procedures.
a) If sampling a body of running water, point the mouth of the bag
upstream and your hand down stream to avoid contamination.
b) If sampling from a water faucet, run the faucet for one minute
before obtaining a sample.
c) Rinse the tap twice with the sample water prior to filling and
collecting.
d) Fill tap as full as possible. Half filling the bottle leaves more
room for oxygen which will promote degradation of your sample.
e) Collect data such as temperature and pH which affect the
solubility of many ions.
For the collection of sample of water, the sample for bacteriology
examination should be taken first to avoid the danger of contamination
of sampling point during the collection of others. Sterilised natural glass
bottle provided with glass stoppers should be used for collection of
samples for bacteriological examination. The stopper and the rest bottles
should be protected by a paper foil e.g. thin aluminum foil.
If the water to be sampled contains or is likely to contain traces of
residual chlorine, it is necessary to add into the sampling bottle before
sterilisation a substantial quantity of sodium trisulphate (Na2S2O3.2H2O)
crystal to neutralise these substance e.g. 0-1m of 3.6 solution of
crystalline Na2S2O3.2H2O to 3.6mg of 100m has no significant effect on
the coliform bacteria in the water. This is generally recommended as a
general practice in sampling collection. When sample of chlorinated
water are taken, it is necessary to determine the content of resident
chlorine (Cl2) that is being sampled.
The sampling bottle should be kept closed until it is required for filling.
The stopper should be removed with care to eliminate soiling and during
160
sampling the stopper and the neck of the bottle should not be filled
without rinsing and stopper replaced immediately.
3.3.1 Collection from Tap
If sample is taken from a tap, it is a distribution system. The tap should
be washed and a quantity of waters allowed to waste for 3-4 minutes or
for a sufficient time to permit cleaning of the service line. The flow from
the pipe should be restricted to permit filling of the bottle without
splashing. Leaking tap which permits water to flow over to the side of
the bottle should be avoided as sampling points.
3.3.2 Collection from Rivers, Streams, Lakes, Reservoirs,
Springs and Shallow Wells
If from any of these sources, the aim must be to obtain a sample that is
representative of the water which will be taken for the purpose of supply
to consumers. It is therefore undesirable for sample to be taken too near
the bank and too far from the point of draw off or at a depth or below
the point of draw.
In a stream, area of relative stagnation should be avoided. Samples
should be taken by holding the bottle near its base in the hand and
plunging neck downward below the surface. The bottle should then be
turned upward, the mouth of the bottle being directed towards the
current. If no current exists in a reservoir, a current should be artificially
created by putting the bottle horizontally forward in the direction away
from the hand. It is not possible to collect sample in this way, a weight
may be attached to the base of the bottle which can then be allowed into
the water. Special device should be produced to enable sample be
collected from depth of lake or reservoir.
3.3.3 Collection from Well Fitted with Hand Pump
Water should be pumped to waste for about 5 minutes before samples
are collected. If there is no pumping-machine, a sample can be collected
directly from the well by means of sterilised bottle with a weight at the
base. This should be done with care.
3.4 Data Needed during Water Sampling
a) Name and address of the person requiring the examination.
b) Reason for the examination, whether routine sampling or
otherwise.
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c) Exact place from which a sample was taken. If taken from a
house top, whether drawn from a cistern or directly from rain.
d) What method of purification and disinfection is used if any, and
at what point is it applied, dosage per litre of the disinfecting
agent used.
e) Whether source: is it well, spring etc.
f) If from a well,
(i) Depth of the well and water level.
(ii) Whether covered or uncovered, nature, materials and
construction of the cover.
(iii) Depth of lining and whether capped.
(iv) Whether newly constructed or with any recent alteration
that might affect the condition of the well.
g) Condition of the weather at the time of sampling and particulars
of any recent rainfall or flood condition.
h) Proximity of drains, cesspools or other pollutants to the source of
the sample.
i) Whether water becomes affected in appearance, colour, or taste
after heavy rain.
j) Temperature of the water at the time of sampling.
k) Date and time when samples were taken and dispatched.
3.5 Preservation and Storage of Sample
The bacteriological examination of samples of water should be initiated
immediately after collection. However such requirement is seldom
practice. The recommendation is that bacteriological examination of
sample should commence not later than one hour from the time of
collection. In case the time between collection and examination exceeds
one hour, the temperature of the sample should be maintained as closely
as possible to that of the sample at time of sampling. The time and
temperature of storage should be recorded and considered in the
interpretation of result. Generally if the examination exceeds a day (24
hours) the following storage conditions should obtain:
(i) Storage before filtration should be at 4 oC for not more than 30
days
(ii) Storage after filtration should be at 4 0C for not more than 30
days
Filtration of the sample through 0.45 um fitters removes most bacteria
and will slow sample degradation. All glassware used for filtration
should also be cleaned using acid washing steps. Acid-washing requires
safety goggles.
162
3.5.1 Cleaning Glassware Used in Analysis
This step serves to oxidise and solubilise any oxidisable materials. Rinse
the inside of the glassware with 8m nitric acid (HN03). Five to 20 ml
acid should suffice. It is not necessary to fill the glassware, just add
enough that you can turn the glassware and wet all internal surfaces. If
the glassware is not visibly dirty and the acid does not discolour you can
reuse the acid for other glassware. Rinse the bottle twice with tap water.
Do not reuse the rinse water. Do a final rinse with three individual
portions of deionised water. Do not reuse the rinse water. Do not dry the
internal surfaces or touch them with hands. All acid must be disposed of
in the acid waste jars provided. Do not pour it down the drain.
Pay special attention to avoid contact with your hands around opening
of the glassware. Reduce accidental contamination of the glassware
exterior which could then be cross- contaminated to the contents during
later handling.
4.0 CONCLUSION
From the above, we can conclude that the purpose of water sampling is
to examine the water in the laboratory, to find out the quality whether
contaminated or not. If contaminated, what the contaminants are, and
where they could possibly have come from and to find out if the
contaminants are pathogenic or not. Efforts of achieving this without
introducing germs during the process by the person doing this were
found necessary.
5.0 SUMMARY
We have been able to see what water sampling is and the need for it in
water quality control measures. Some of the purposes are: it aims at
making sure that the quality of water that gets to the tap of the
consumers is wholesome, and to determine the extent of treatment that
should be given to a given source of water for a given purpose.
We also treated the sampling points suitable for collection of samples
and the basic requirements for collecting water sample and the
procedure for sampling. Furthermore, methods of collecting samples
from different sources were mentioned just as data needed, preservations
and storage of samples were treated.
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6.0 TUTOR-MARKED ASSIGNMENT
1. (a) Define water sampling technique and explain the need for
water sampling.
(b) Enumerate the basic requirements in collecting water
sampling.
2. (a) List the data needed during water sampling.
(b) Why the need for preservation and storage of sample?
7.0 REFERENCES /FURTHER READING
Ebisike, A.O. et al. (2009).The Sanitarian and his Work. Ibadan:
Juaainchrist Printers.
Heald, D. (2009). Water Science, Bramh, Water Resource Management
Division.
Nnaj,i E. (1990). An unpublished Lecture on “Water Supply and
Sanitation”
Delivered at School of Health Technology, Oji River.
West Africa Health Examination Board (1991). Water and
Building Sanitation. Ibadan: Sterling Publishing Consult.
Wikie, W. (1965). Jordan’s Tropical Hygiene and Sanitation. (4th
ed.).
United Kingdom: Bulsie Turndal and Co.
164
UNIT 4 WATER SUPPLY AND DISTRIBUTION
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Water Supply
3.1.1 Meaning and Concepts of Water Supply
3.1.2 Sources of Water Supply
3.1.3 Water Supply Service Provisions
3.1.4 Factors Affecting Water Supply in the Community
3.1.5 Protection and Improvement of Water Supply in
Developing Countries
3.2 Water Distribution
3.2.1 Meaning and Concepts of Water Distribution
3.2.2 Design and Construction of Pipelines
3.2.3 Pipe Materials and Sizes
3.2.4 Water Distributions Systems
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/Further Reading
1.0 INTRODUCTION
In order to live well and overcome most of waterborne and water-related
diseases there should be adequate water supply which comes from
different sources. Whichever source, deliberate intervention reflected by
way of treatment is always given to achieve water portability. When the
above is achieved and in a bid to serve many people, there arise the need
for its distribution. To supply water is to make it available and when a
lot of people are to be served, its distribution becomes compulsory.
Therefore on a large scale of operations water supply and distribution
must always go together. This is the subject of this unit.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
discuss the meaning and concepts of water supply
enumerate the sources of water supply
explain water supply service provisions
list factors affecting water supply
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165
explain the protection and improvement of water supply in
developing countries
know the meaning of water distribution and its processes
list pipe material and sizes
mention water distribution systems.
3.0 MAIN CONTENT
3.1 Water Supply
3.1.1 Meaning and Concepts of Water Supply
Water supply is the provision of water by public corporations,
commercial organisations, community endeavours or by individuals,
usually through a system of pumps and pipes (Wikipedia). In other
words, it is the making of quality water available to the people.
Public health officials believe that the health benefits derivable from the
construction of water supply systems are considerably reduced unless
water is made readily available not only for drinking purposes but also
for domestic use and the improvement of personal hygiene.
Each community needs a safe and adequate supply of water. According
to Lucas and Gilles (1984), water supply technologies need to be
technically and environmentally sound, economically efficient,
financially affordable, and acceptable to the users from the social,
cultural and political stand points. They need to be simple in design and
easy to install, operate and maintain.
The objectives of any water supply system, according to WAHEB
(1991) are:
1. to supply safe and wholesome water to the user, whether these
constitute a family, a group of families or a community
2. to supply water in adequate quantity
3. to make water readily available to the users in order to encourage
personal and house hold hygiene.
It should be noted that safe and wholesome water can be defined as that
which will not produce harmful effects upon consumptions. Again,
according to WAHEB (1991), it is:
(i) that which is uncontaminated and hence unable to infect its user
with any waterborne diseases
(ii) free from poisonous substances
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(iii) free from excessive amount of mineral and organic matter.
The first step in designing a water supply system is to select a suitable
source or combinations of sources of water. The source must be capable
of supplying enough water for the community. If not, another source or
perhaps several sources will be required. This then takes us to the next
level which is sources of water supply.
3.1.2 Sources of Water Supply
There are three sources of water supply, namely:
(a) Rainwater- collected in cistern
(b) Underground water which include the wells and springs
(c) Surface water which include dams, lakes, streams, river, sea etc.
The growth in population and the increasing use of streams and other
bodies of water for the disposal of waste have been detrimental to water
supplies, particularly to surface supplies and to a lesser extent
groundwater. There is increasing concern about water supplies since the
amount available in any area is determined by rainfall, geology,
topography and geography.
The choice of the source depends on local circumstances. Where a
spring of sufficient capacity is available, this may be the most suitable
source of supply. Where springs are not available or not suited to
development, generally the last option is the ground water sources. For
small supplies, simple prospecting method will be adequate. For larger
supplies, more extensive hydro-geological investigation using special
methods and techniques are likely to be needed. Infiltration drains may
be considered for shallow groundwater sources. Dug wells can be
appropriate for reaching groundwater at medium depth. Boreholes are
generally most suitable for drawing water from deeper water bearing
ground strata. Dug wells are usually within the local construction
capabilities. Drilling of boreholes requires more sophisticated equipment
and skill. If groundwater is not available or digging a well or drilling a
borehole will be expensive, surface water sources should be considered.
However, treatment is likely to be necessary to render it safe for human
consumption. Where rainfall pattern permits, rainwater harvesting will
be ideal. This can serve households and small communities.
From all the above, we can say that water supply system get water from
a variety of locations, including groundwater (acquifer), surface water
(lakes and rivers), conservation and the sea through desalination. The
water is then in most cases, purified, disinfected through chlorination
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and sometimes fluoridated. Treated water then either flows by gravity or
is pumped to reservoirs.
Emergency supplies when necessary should be made available from
suitable source of distribution to consumers. It may involve temporarily
increasing the capacity of the existing transmission mains.
3.1.3 Water Supply Service Provisions
Water supply service providers, which are often utilities, differ from
each other in terms of their geographical coverage relative to
administrative boundaries, their sectoral coverage; their ownership
structure and their governance arrangement.
(a) Geographical coverage
Many water utilities provide services in a single city, town or
municipality. However in many countries, municipalities have
associated regional or inter municipal or multi-jurisdictional utilities to
benefit from economies of scale. In some federal countries there are
water service providers covering most or all cities and towns in an entire
state, such as in all states of Brazil and some states in Mexico. Some
smaller countries especially developed countries have established
service providers that cover the entire country or at least most of its
cities and major towns. Some of these are found in West African
Countries.
(b) Sector coverage
Some water utilities provide only water supply services, while sewerage
is under the responsibility of a different entity. This is the case in
Tunisia. However in most cases water utilities also provide sewer and
wastewater treatment services. In some cities or countries utilities also
distribute electricity. Multi-utilities provide certain benefits such as
common billing and the option to cross-subsidise water services with
revenues from electricity sales if permitted by law.
(c) Ownership and governance arrangements
Water supply providers can either be public, private, mixed or co-
operative. Most urban water supply services around the world are
provided by public entities. As William Alexander, Prince or Orange
(2002) states, “The water crisis that is affecting so many people is a
crisis of governance not of water scarcity. The introduction of cost-
reflective tariffs together with cross-subsidisation between richer and
poorer consumers is an essential governance reform in order to reduce
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the high levels of unaccounted water (UAW) and to provide the finance
needed to extend the network to those poorest households who remain
unconnected.” Partnership arrangements between the public and private
sector can play an important role in order to achieve this objective
(Nickson and Francey, 2003).
(d) Private sector participation
An estimated 10 percent of urban water supply is provided by private or
mixed public-private companies, usually under concessions, lease, or
management contracts. Under this arrangement the public entity that is
legally responsible for service provision delegates certain or all aspects
of service provision to the private sector provider for a period typically
ranging from four to 30 years. The public entity continues to own the
assets. These arrangements are common in France and Spain. In some
parts of the world, water supply systems have been completely sold to
the private sector (privatisation) e.g. England, Wales and Chile. In
recent years, a number of cities have reverted to the public sector in a
process called “remunicipalisation.
3.1.4 Factors Affecting Water Supply in the Community
These are the factors that could affect water supply, that is, factors that
exert effect on the supply of water to a community either at the stage of
its provision, operation and maintenance.
These factors are:
(i) cultural acceptance
(ii) dependability
(iii) quantity
(iv) quality
(v) cost
(vi) proximity to users
(vii) power requirement
(viii) maintenance requirement/lack of appropriate technology
(ix) training requirement for water supply.
(i) Cultural acceptance: Some communities due to their cultural
beliefs reject some water sources even where they are naturally
available. An example is a village called Zama which rejects water from
a nearby stream for the mere fact that Juju traditionally called ‘Dodo’
comes from the rivers to dance and punish defaulters in the community.
There are other numerous beliefs that make other communities do the
same.
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(ii) Dependability: This factor affects water supply in the sense that
certain communities rely on a source of water which could dry up
easily leaving them with little or no water to meet their needs or
even in times of contamination, they are forced to take unsafe
water because there is no alternative source of water.
(iii) Quantity of water: In some communities, water source may not
be available at all in that they are forced to consume any water
seen whether polluted or not or travel to distant places before
they are able to obtain water.
(iv) Quality of water: Some communities especially those using
rivers have their rivers heavily polluted in that the people are
frequently affected by waterborne diseases most especially in the
rainy season. Even with the abundance of such rivers some can
still look for better options.
(v) The cost: The cost of constructing and maintaining sanitary and
adequate water in some communities is so much that the
community has to make do with any kind of water in the
community.
(vi) Proximity to users: Water sources for some communities are
very far that it takes a lot of time and hardship for the community
to obtain water. This is common in villages on hilly areas that
have to go to rivers to obtain water from the valley.
(vii) Power requirement: This affects water supply in a community
due to the fact that some water sources like springs, rivers or
even bore holes have water that is difficult to bring out. Where
pumps are not available, boreholes become useless because the
water cannot be pumped for the community.
(viii) Maintenance requirement/lack of appropriate technology: Certain communities may be favoured by government or any
other agency by being provided with good water source e.g.
borehole. Due to insufficient maintenance or lack of it, such
source fails to yield the needed result. Also, some communities
may be provided with the type that the villagers may not know
how to operate because of the technicalities involved. Where this
is the case, the purpose is defected thus, subjecting them to
scarcity.
(ix) Training requirement for water supply operation: In order to
operate machines and repair any faulty part therefore, adequate
170
training is needed. In communities where this adequately trained
machine operators are lacking, the use of engines, mono pumps
etc may be difficult to operate with the result that water supply
will be impaired.
Perhaps, for some or all of the above factors the Federal Government of
Nigeria (2000) noted that water supply services where they exist are
unreliable and of low quality and are not sustainable because of
difficulties in management, operation and pricing and failure to recover
costs. Furthermore, many water supply systems show extensive
deteriorations and poor utilisation of existing capacity due to under-
maintenance and lack of funds for operations.
According to Wikipedia, continuity of water supply is taken for granted
in most developed countries, but is a severe problem in many
developing countries where sometimes water is only provided for a few
hours every day or a few days a week. It is estimated that about half of
the population of developing countries receive water on an intermittent
basis.
3.1.5 Protection and Improvement of Water Supply in
Developing Countries
In compliance with the drinking water quality standard based on WHO
minimum standard which aims to provide assurance that the supplies is
safe, adequate management is essential to ensure continuous compliance
and there are many potential situations some of which can be arrived so
quickly at what could cause potential and hazardous situation. Potential
problem can be protected by safeguarding the overall watershed by
proper maintenance and inspection of the treatment plant and
distribution system. This can be done by training managers and plant
personnel and by consumer’s education. However, it is essential that
water suppliers periodically do the following as stated by Ude (2003).
1. Re-assess their operation to ensure that conditions that could
affect the quality of water have not changed.
2. Periodic maintenance is performed.
3. Repairs and renewal of equipments are undertaken on time
without delay.
4. Personnel are adequately trained.
5. Job skills are maintained.
In order to supply good quality water to large communities or towns,
Njoku (1978) recommends the following:
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171
1. If there is a river, a concrete wall should be built half way across
it to collect more water so that the water level may rise. If there is
no river, a number of wells and springs can be used.
2. A reservoir higher than all the houses which get water from it
should be built, so that pipes can be fixed in any room which
needs them.
3. There should be a great pumping machine for lifting the water to
a height and storing it in the reservoir higher up on the hillside.
4. Great filters should be built so that the water is purified before it
reaches the reservoir.
5. If the water is hard, something which makes the water soft while
it is in the reservoir should be added. Also chlorine gas (tolerable
and adequate quantity) may be added to kill micro-organisms at
the rate of a point to one million pints of water.
6. The water can be brought to the towns through pipes about 25
centimetres in width. It can be channeled to the streets through
small pipes.
3.2 Water Distribution
3.2.1 Meaning and Concepts of Water Distribution
Water distribution simply means the processes or means through which
water from a source is supplied to the desired consumers at different
locations. Water distribution system is composed of the pipes, valves,
holding tanks and pumps which supply water to its end use points at the
required flow rates and pressure. Water connections should be located to
limit hose length to 60feet. Pipes must be sized so that pressure drops
due to frictions are not excessive (Reinemann, 2004).
According to Godman and Gutteridge (1979), water is distributed to
house by water mains. For the benefit of houses without a piped supply,
and in undeveloped areas of towns, water is supplied by stand pipes.
Stand pipes are built with a concrete or brick base so that any excess or
waste water does not change the surrounding earth into mud and thereby
make it an excellent breeding ground for germs. For distributions,
pipelines are used and pipes are preferred because they do not colour
water, produce no taste or odour and are durable (WAHEB, 1991).
If any source of water has yield which does not meet the peak flow
requirements of the system, a pressure tank can be installed to provide
peak flow demands. A pressure tank provides a small amount of storage,
usually 10- 30 percent of the tank size. This provides a small amount of
water without starting the pump. It also helps satisfy water needs during
short peak use periods. When the water source and pressure tank cannot
172
deliver the required flow rate, an intermediate storage and two-pump
system can be used. Intermediate storage also facilitates water reuse,
which can significantly reduce total water quantity requirements. The
first pump, usually the well pump has a low level cut-off and a capacity
slightly less that the well yields so as not to pump the well dry. This
pump fills an intermediate storage with water for peak use periods. A
second pump draws the water from the intermediate storage and forces it
into a pressure tank. Intermediate storage can be plastic, concrete or
steel tanks which protect the water from contamination. The
intermediate storage may be elevated to avoid the use of pressure tank
and second pump.
3.2.2 Design and Construction of Pipelines
To do this effectively, the following should be observed and done as
adopted from WAHEB, (1991).
A topographic map should be produced showing the location of
the pipeline, other relevant structures and the profile of the route
to be followed.
The location of the pipeline should be such that will reduce
construction costs and internal pressures. Install pressure relief
valves where necessary.
The pipeline should be laid along the shortest route possible.
Change in direction should be made by gradual alternation in
pipe directions at the joints.
The intake should be located at a distance from the shore to
minimise pollution. A strainer should be fitted at the inlet of the
pipe to prevent entrance of fish or debris.
Each pipe should be built to protect against injury from traffic
and weather conditions at least 12|| (Twelve inches) or 30cm
below the ground level.
Each pipe should be inspected before it is laid to detect cracks
and damaged coating.
Newly laid pipelines should undergo hydrostatic tests for at least
24 hours to detect leakage.
Pipelines should be disinfected before they are put into service as
they might be contaminated in the course of construction.
The system should be designed to provide an adequate supply at
adequate pressure to all parts f the system.
The portability of the water should not be impaired by defects in
the system.
Sufficient valves and washouts should be provided to permit
repairs without undue interruption of service.
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3.2.3 Pipe Material and Size
The types of pipes generally used in water systems are galvanised steel,
copper and plastic. Galvanised steel pipe is suitable for all piping inside
buildings. Plastic and copper are preferred for underground installations.
Highly mineralised water greatly reduced the life of steel pipe.
General design rules of thumb for pipe sizing are that friction loss
should not exceed five psi from the pressure tank to the service entry
and should not exceed 10psi from the pressure tank to any isolated
fixture. The criterion is generally met if peak flow water velocities are
limited to four feet per second. According to Reinemann (2004), the
water flow rate in gallons per minute that produces this velocity for
various pipe sizes are given below.
Water flow rate (gpm) pipe material
Nominal pipe size steel copper plastic
½11
3 2 3
3/411
6 6 6
111
10 10 10
1 1/41I
18 14 18
1 1/211
25 20 25
211
40 35 40
2 1/211
50 - 50
311
90 - 100
411
140 - 140
Source: (Reinemann, 2004)
The above information should be used only as a rule of thumb to
estimate pipe sizes. The pipes in the distribution systems should meet or
exceed the minimum requirement of the national plumbing codes and
local codes. The plumbing contractor should be provided with a list of
all intended tasks and equipment that will use water and the physical
location of end use. Equipment manufacturers can provide water
quantity and flow requirements for their equipment.
3.2.4 Water Distribution Systems
There are two main system of distributing water. Namely:
(a) The gridiron system
(b) The dead-end system.
174
The gridiron system: In this system, the extremities of the pipes are
connected. This enables water to circulate continuously throughout the
distribution system.
The dead-end system: Pipes are not connected at the extremities, as it
is expected that water will be delivered at the end of the pipe serving a
particular area or district.
4.0 CONCLUSION
Water supply and distribution play vital roles in the life of man how and
to maximise its gain has been adequately discussed in this unit. Just as
the sources of water supply are needed to be handled properly and
supplied in a reasonable quality and quantity, so do we need to handle it
during its distribution to make a perfect match.
5.0 SUMMARY
In this unit, we have been able to know how water is supplied to
individuals and communities and from different sources such as
rainwater, underground water and surface water. We also learnt that the
source used depends mostly on the number of users and affordability.
Water supply provision which included geographical coverage, sector
coverage, ownership and governance arrangement and private sector
participation were discussed. Equally discussed were factors affecting
water supply and ways of improving same in communities.
Another part in this unit discussed was about water distribution. We
were made to know that distribution system is like a circulation system
of the human body. It ensures that water is distributed to places needing
it at all times and in a harmless condition.
6.0 TUTOR-MARKED ASSIGNMENT
1 (a) List the objectives of any water supply system.
(b) Enumerate sources of water supply and explain any one of
them.
(c) List the factors affecting water supply.
2 (a) Define Water Distribution.
(b) Outline things to be observed and done while designing
and constructing pipelines.
(c) List the main water distribution system you know.
EHS 304 MODULE 3
175
7.0 REFERENCES/FURTHER READING
Federal Republic of Nigeria (2000). Water Supply and Sanitation
Strategy Note.
Godman, A. & Gutteridge, A.C. (1979). A New Health Science for
Africa. London:Longman Group Limited.
Lucas, A.O. & Gilles, H. M. (1984). A Short Textbook of Preventive
Medicine for the Tropics.(2nd
ed.). London: Hodder and
Stoughton.
Nickson, A. & France, R. (2003). Tapping the Market: The Challenge of
Institutional Region to the Urban Water Sector.
Njoku, P. A. (1978). Certificate Health Science and Health Education
for Schools and Colleges. Onitsha: Africana Educational
Publishers.
Reinemann, J. D. (2004). “Water Supply and Distribution.” University
of Wisconsin Madison, Milking Research and Instruction Lab.
www.uwef. Edu/uwnirl
Ude, B. C. (2003). “Water supply and Drainage” Being an unpublished
Lecture delivered at the Department of Architecture, University
of Nigeria, Enugu.
West African Health Examination Board (WAHEB) (1991). Water and
Building Sanitation. Ibadan: Sterling Publishing Company.
Wikipedia, the Free Encyclopedia.
http://www.tni.org/tnibook/remunicupalisation.Transnational
institute/municipal services project/corporate European
observatory.
176
UNIT 5 ENVIRONMENTAL PROBLEMS OF WATER
DISTRIBUTION
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Environmental Problems of Water Supply and Distribution
3.2 Causes of Environmental Problems of Water Supply
Distribution
3.3 Impacts or Effects of Environmental Problems
3.4 Remedies of Identified Problems
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/Further Reading
1.0 INTRODUCTION
In our last section, we saw water supply and distribution to people
outside the area of water source. In this section, we shall discuss
environmental problems of water supply and distribution with a view to
finding their causes, impacts and proffer possible remedies to the
identified problems.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
discuss environmental problems of water supply and distribution
enumerate the causes of environmental problems of water supply
and distribution
explain the impacts of environmental problems
proffer solutions to the identified problems.
3.0 MAIN CONTENT
3.1 Environmental Problems of Water Supply Distribution
A lot of problems which are environmentally related affect water supply
and distribution as can be seen below.
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(a) Inadequate quantity of drinking water supply: Inadequacy of
safe drinking water supply is the foremost of several
environmental problems. Diseases spread owing to poor hygiene.
Ability to maintain clean environment become increasingly
difficult with insufficient safe water. Blockage of sewerage
system and spreading of sanitary waste on open surfaces pollute
the soil, water and even air. The problem of inadequate drinking
water supply is more acute in drought prone areas generally and
higher urbanisation has increased the task of providing drinking
water and basic services to people..
(b) Scarcity based on seasonality of flow: Water scarcity or limited
availability, particularly during the summer months in Karnata,
India or dry seasons in Nigeria and Niger Republic result in
fluctuations, irregularity and reduction in per capita availability.
Fluctuations in water supply cause unexpected water
contamination in distributional network. This is attributable to
rustiness developed in pipes due to reduced water flow which
leads to health and environmental problems. Borehole and well
water supply schemes most times too are seasonal with
fluctuations in their characteristics.
(c) Depletion of groundwater: Depletion of drinking water sources,
be they ground or surface, accentuates environmental problems
through water shortage and quality deterioration. Drastic decline
in groundwater table creates the risk of drinking water shortage.
As observes by Kajamarthama (1998), fluctuation and depletion
of groundwater level can occur up to seven metres in several
districts.
(d) Deteriorating drinking water quality: Water which is tasteless
and free from odour, colour and organic and inorganic
contamination is considered as safe drinking water. Drinking
water quality has been determined by the presence of certain
organic and inorganic substances in excess of tolerance limit.
Unsafe and poor quality water adversely affects health status of
people. For example, chemicals like fluoride in excess quantity
(more than 1.5ppm) cause dental and bone hazards while skin
rashes result by consuming water with excess brackishness. Also
biological or organic contamination of water gives rise to
waterborne diseases.
(e) Discernment of the direction of surface flow: Is difficult owing
to the high degree of landscape alteration. This occurs as a result
of the effect of urbanisation.
(f) Density and connectivity of the flow channel: Have been
severely altered due to construction of buildings and roads. This
affects water distribution mainly.
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3.2 Causes of Environmental Problems of Water Supply and
Distribution
(a) According to Puttaswamaiah, environmental problems in
drinking water supply are caused by both supply and demand side
factors. Two major supply factors are depletion and deterioration
in water quantity and quality which are aggravated by demand
factors like over extraction and pollution as they are
interdependent.
(b) Furthermore, major environmental factors causing inadequate
drinking water supply include non-availability of perennial water
sources and high dependence on groundwater in most places due
to geographical and geological conditions, rainwater fluctuation,
low recharge rate etc. It is important to note that over extraction
also contribute significantly to this depletion.
c) The rapid and accelerated drawing of groundwater to meet
competing demands from agriculture, industry and other sectors
has led to decline in the groundwater table.
(d) Increasing demand and over-exploitation are the other demand-
based causal factors leading to inadequate drinking water
availability. Groundwater extraction is growing rapidly as it is
used for drinking, irrigation and industrial needs.
(e) Besides the above supply and demand driven factors, lack of
operation and maintenance of water supply schemes (a matter of
management and governance) is another important cause for
inadequate drinking water supply (Gok, 2000).
(f) A very important cause which is management related is leakages
in the distribution network. The leakage occurs mainly due to
corroded pipes in distribution networks; damages caused during
road widening and repair works; and use of poor quality pipes in
majority of household connections.
(g) Drinking water apart from source level is also likely to get
contaminated in the distribution network when sewage or other
waste materials enter through broken or leaking pipe.
(h) Furthermore, improper siting of water collection points
particularly in low lying areas, unhygienic practice of collecting
water by household etc. adversely affect water quality.
3.3 Impacts or Effects of Environmental Problems in
Drinking Water Supply
(1) Generally, environmental problems in drinking water supply and
distribution impact significantly on health status of people and
other resources like water and land. Consumption of unhygienic
water results in waterborne diseases, like: scabies, fungal
EHS 304 MODULE 3
179
infections, trachoma etc. Many rural communities are facing
health problems due to inadequate water use.
(2) Inadequate water use further creates blockage in sewage flow
which could contaminate water sources.
(3) Irregular water supply causes pollution in distribution pipes due
to rusting and back – syphonage of water because of low pressure
and insufficient water flow.
(4) Apart from health effects, inadequate water supply increases
hardship on women and children compelling them to spend more
time and energy in collecting water.
(5) Impact of water loss in the distribution system would be severe
on the poor and people living in outlying areas.
(6) Impact of depleting water resources, can be seen in decreased
water availability as witnessed in many states and countries in
recent years due to continued spell of drought. Decline in
groundwater level has resulted in collapse of many of the already
created drinking water supply schemes.
3.4 Remedies of Identified Problems
From all that have been seen above, it is evident that majority of the
environmental problems are caused by both natural and human made
factors. Decline in quantity and quality of water has serious implication
on health and environment as discussed in this unit. Considering the
status and problems in drinking water supply the following points might
be considered to resolve problems and augment services.
i) Partially covered habitations in both rural and urban areas should
be brought under full coverage of water supply.
ii) Drought prone districts or areas should be given high priority to
resolve the problem of inadequate water supply.
iii) Communities with drinking water challenge should be taken on
first priority basis to provide safe drinking water, through
alternative sources or by treating their water.
iv) Operation and maintenance is a major problem in water supply
system, hence priority needs to be attached to these activities for
efficient working of the system.
(v) Privatisation of operation and maintenance of water supply
scheme may offer a better option. But protection should be given
to poor and vulnerable groups in villages.
(vii) Maintenance of water quality is an important issue. A single
water quality testing agency should be provided for both rural
and urban areas. Its operations should be widely publicised. A
vigilante group might also be created to report on quality and
180
quantity of water supplied, and the operation of the water supply
system.
(vii) Protection should be given to the pipes laid and used for water
distribution.
(viii) After main road construction, care must be taken to install all
installable and maintain same.
(ix) Water quality awareness camps should be promoted particularly
in rural areas where ground water quality is a serious problem.
(x) Attention should be given to dual water supply system in water
quality affected areas - one for drinking and another for washing,
bathing and cleaning purposes.
(xi) Measures need to be initiated and implemented against water
polluting industries and laws promulgated to penalise defaulters.
(xii) An integrated institutional system for ground water conservation
and recharging measures needs to be promoted to conserve the
major source of drinking water.
(xiii) Institutional initiatives need to be promoted for rainwater
harvesting in both urban and rural areas.
(xiv) Utilisation of treated waste water needs to be promoted for
purposes like industrial and gardening activities, for which
incentives in terms of subsidised price may be considered.
4.0 CONCLUSION
From the above, one can conclude that environmental pressures are
rising on drinking water sources - both ground and surface - and also in
the distribution system. These have created problems of depletion and
deterioration of quantity and quality of water. The above are caused
majorly by the supply and demand factors as seen above. The effects of
the foregoing are on man’s health and his environment. Solutions
abound to remedy the situation.
5.0 SUMMARY
In this unit, we learned about the environmental problems of water
supply and distribution. Some of these include: inadequate quantity of
drinking water supply, scarcity based on seasonality and depletion of
groundwater.
The problems are caused by a variety of supply and demand factors.
Over extraction and pollution are some of the demand factors while
depletion is an example of supply factor. The effects or impacts of
these problems centre more on our health and the environmental itself. It
equally increases the suffering of women and children as they suffer a
lot just to get potable water.
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Solutions abound to tackle them which if followed to the letter will
make good the bad situation.
6.0 TUTOR-MARKED ASSIGNMENT
1. Enumerate the environmental problems of water supply and
distribution.
2. List all the causes of environmental problems of water supply and
distribution.
3. Mention the impacts of environmental problems of water supply
and distribution.
7.0 REFERENCES / FURTHER READING
Gleick, P. H. ( 1998). “Water and Human Health in Water Resources
and Economic Development.” In: R. Maria Seleth (Ed.).
Government of Karnataka (2000). Rural Water Supply and Sanitation in
Karnataka - Strategy Paper 2000-2005. Bangalore: Rural
Development and Pomchayat Raj Department.
Puttaswamaiah, S. (n.d.) Drinking Water Supply: Environmental
Problems, Causes, Impacts and Remedies - Experiences from
Karnataka.
Rajamarthanda (1998), Behaviour of Depth to Water Level between
1998-47 in Karnataka State. Bangalore: Dept of Mines and
Geology.
United Nations Development Programme (2003). Human Development
Report 2003: Millennium Development Goal - A Compact among
Nations to End Human Poverty. UNDP.
MODULE 3
Unit 1 Physical, Chemical and Biological Principles of Water
Treatment
Unit2 Public Health Importance of Water
Unit 3 Urban and Community Storm Water Management
Unit 4 Drainage Layout
Unit 5 State and Federal Regulatory Standards
182
UNIT 1 PHYSICAL, CHEMICAL AND BIOLOGICAL
PRINCIPLES OF WATER TREATMENT
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 The Need for Water Treatment
3.2 Levels of Water Treatment
3.3 Conventional Water Treatment / Purification
3.3.1 Physical Principle Involved in Water Treatment
3.3.2 Biological Principle Involved in Water Treatment
3.3.3 Chemical Principle Involved in Water Treatment
4.0 Conduction
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References /Further Reading
1.0 INTRODUCTION
You will recall that water in nature undergoes the hydrological cycle by
which energy from the sun evaporates water from surfaces of oceans,
rivers, lakes and moist ground. This later precipitates and falls as rain,
snow, dew or hail. Part of these precipitates percolates into the ground
to form underground water. Others flow over the surface of the earth to
form streams, lake, rivers, seas and oceans.
At each stage of the hydrological cycle significant changes occur in the
quality of water. This water dissolves organic materials, gasses,
minerals and also carries in suspension fine particles of soil,
vegetation and dust. In determining the portability of water, whose
source may be from rain fall, surface or underground; the whole
cycle of natural water, with the added effects of human activity
should be taken into consideration. The above scenarios inform the
birth of water treatment. Water treatments take physical, biological and
chemical processes as we will see shortly.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
discuss the need for water treatment
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183
explain the categories or levels of
mention the conventional water treatments
highlight the physical, biological and chemical principles
involved in water treatment.
3.0 MAIN CONTENT
3.1 The Need for Water Treatment
According to WAHEB (1991), water plays a predominant role in the
transmission of certain waterborne diseases. It plays the passive vehicle
for infecting agents of such diseases like cholera, typhoid etc. More so,
according to Njoku (1978), water contains impurities which
contaminate and or pollute the water bodies making them unwholesome
for use.
The objective of water treatment or purification is to supply safe and
wholesome water to the users whether as members of a family, group of
families or a community. Safe and wholesome water is that water which
does not cause harm to its users. According to Fair and Geyer (1963),
wholesome water is that which is:
uncontaminated and hence unable to infect its users with any
waterborne disease
free from poisonous substance
free from excessive amount of minerals and organic matters.
3.2 Levels of Water Treatment
WAHEB (1991) states that the totality of operations or methods
employed in making raw water potable are collectively known as water
purification or treatment. The level of this treatment depends to a large
extent on the scale of the water to be treated, the financial status of
those wanting to treat the water, the use to which the treated water is
to be made and the availability of the needed skill for such treatment
(Nnaji,1990).
There are two main types or levels of water purification or treatment.
a) Domestic water treatment
b) Conventional water treatment (Nnaji, 1990).
Before dealing with the conventional water treatment it will be proper to
explain some of the methods employed in domestic water treatment. .A
critical look at them will show that the principle behind them is
chemical, physical or biological process.
184
(1) Protection of the sources of water: The protection of the source
of water should be the concern of all those interested in the
purification or treatment of water. It is of particular importance
that sources of water should be protected from pollution from
human being and animals and even from inanimate objects.
Protection is done at all levels.
(2) Boiling: Boiling is a common method of water purification
employed widely in homes especially during an emergency like
epidemic of waterborne disease. The effectiveness of boiling is
due to its ability to destroy pathogenic organisms provided water
is at boiling point of 100o
C for at least 10 minutes. The water so
boiled is cooled very quickly and stored in clean containers.
(3) Addition of chemicals: Chemicals like Alum and Milton are
added to water as means of purification. Some of these
chemicals cause the coagulation of dirt which settles at the base
of the container whereby the top part of the water which is now
fairly better is used. Mostly the colour is the thing dealt with
while some micro organism that may remain attached with the
colloids will equally be ridded off during coagulation. Water
treated this way can be boiled again for more purity.
(4) Filtration: Here, the desired water passes through an instrument
which can be cloth or a trek filter and the residues remain on top
of the cloth. Mostly macroscopic particles (visible with unaided
eyes) are the target, though some micro organism attached
with the residue might be eliminated. This method though
not very reliable is able to reduce the bacteria content of water
and remove such organisms as Cyclops. It is commonly practised
in camp in emergency and rural areas.
(5) Chlorination: This involves the addition of a small amount of
chlorine in quantity of water for the purpose of ridding it of
pathogens at domestic level (Wilkie, 1965).
(6) Storage: The essence of storage is to allow natural settlement of
colloidal water to have its solutes settle at the base of the
container and carefully the top water will be poured into another
container for a better use. This equally deals with contaminants at
naked eyes level but not microscopically.
SELF-ASSESSMENT EXERCISE
i. Get some quantities of water from surface runoff after rain and a
pond nearest to you.
ii. Apply any of the above methods for some time and then compare
the results with the initial samples.
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3.3 Conventional Water Treatment (Water Treatment Plant)
This is the method through which large quantities of water is treated for
supply to the public. Its operation is on a large scale. According to
(Nnaji, 1990), certain things are first considered under this method.
These are:
i Source of water: The services of geologists are employed to
ensure that the source of water is a continuous one.
ii Cost and type of treatment: Sources of water that are mostly
cheap in treatment and large in quantity should be used but if
there are no other alternative the available source should be
used, though it may be very costly.
Processes of Conventional Water Treatment
The stages or processes involved in dealing with this depend on the
sources and level of expected impurities or conditions (Godman and
Gutteridge, 1979). Generally however, the following processes can be
employed in conventional water treatment as offered by WAHEB
(1991).
Treatment of water
Source: (WAHEB, 1991)
The above processes end up in giving someone potable water, thus the
water is treated. The principles involved can be categorised into three, as
given below.
i. Physical principle e.g. screening, aeration, coagulation,
sedimentation.
ii. Biological principle e.g. filtration.
iii. Chemical principle e.g. chlorination.
3.3.1 Physical Principles involved in Water Treatment
Under this we have screening, aeration, flocculation, and sedimentation.
a) Screening: This is employed when the source of water supply is
from surface water like stream and rivers. Under this, screening
Chlorination Filtration Sedimenta
tion
Coagulation/
Flocculation Aeration Screening
186
before other treatment method is considered necessary. The
purpose of doing this is to eliminate fish and other aquatic
animals and leaves from damaging the intake pipes. A vertical or
bar screen may be used and after, the debris is removed.
b) Aeration: The purpose of aeration is to restore oxygen to water
devoid of same. Water devoid of air lacks oxygen which makes it
have flat taste. To correct this, oxygen is restored by aeration.
Hence not all raw water requires aeration. Aeration also helps to
release taste and other odour-producing substances (e.g.
hydrogen sulphide) and other volatile substances liberated by
algae growth or as a result of decomposition of organic matters.
Aeration is employed to provide oxygen from the atmosphere for
the oxidation of iron and manganese and to oxidise hydrogen
sulphide and liberate carbondioxide from water. In this way it
prevents corrosion. In achieving proper aeration maximum
surface area of exposure of water to the atmosphere is required to
provide agitation to aid diffusion and to ensure free flow of the
atmosphere to remove gasses and volatile substance liberated
from water (Cox, 1969).
According to Oluwande (1983), aeration devices for convenience
purpose can be grouped into four. These are:
i Spray aerators
ii Cascade (gravity ) aerators
iii Diffused aerators
iv Mechanical Aerators.
Spray Aeration: In this device, the raw water is sprayed into the
atmosphere in thin layer thereby enabling oxygen in the air to come in
contact with the water molecule.
Gravity aeration: Water is allowed to flow over steps. The amount of
aeration that takes place is determined by the period of time during
which aeration takes place.
Diffused air aeration: By this process, air is bubbled into the water
through perforated plates thereby allowing much oxygen to diffuse into
the water.
C) Coagulation /Flocculation: The aim of coagulation or
flocculation is to get the impurities in water to a condition that
will enable them settle down or be removed. Many colloids,
suspended materials or some dissolved solids which cause colour
and turbidity in water cannot on their own settle no matter the
EHS 304 MODULE 3
187
length of time the water is allowed to settle. Substances like
aluminum sulphate (alum) have the quality of attracting together
colloidal substance to form larger particles to such a size that
they become heavy and settle rapidly. Such substances are known
as coagulants and the process is known as “coagulation”. There
are some other substances called “Coagulant Aids” which enables
coagulants to be more efficient by ensuring the formation of
heavier and tougher flocs, e.g. activated silica, limestone,
activated carbon, bentonite etc.
Good coagulation require a proper amount of the coagulant,
optimum pH value; efficient mixing of the coagulant with water
and after the rapid mix, a slow mix, sometimes called “
flocculation” which encourages formation of floc masses and
their absorption of colloids and suspended particles (Ehlers and
Steel, 1965).
D) Sedimentation: This occurs in the sedimentation chamber. In
this chamber, well defined particles settle and the body of the
water is allowed to be quiescent so as to allow particles that have
not settled earlier on to settle resulting in thick sediments at the
bottom of the chamber.
This is the process by which the particles heavier than the liquid, in
which they are contained, gravitate to the bottom of the medium.
Suspended particles in water including some pathogenic organisms
settle to the bottom of a well constructed sedimentation tank, provided
enough time is allowed for this to happen. Plain sedimentation in
impounded reservoirs can lead to the reduction in turbidity and bacteria
content especially pathogenic bacteria in water.
3.3.2 Biological Principle involved in Water Treatment
Filtration: The figure below shows a sand filter bed used for filtration.
188
Fig. 1.1: Sand Filter Bed
Source: (WAHEB, 1991)
Following the stages of water treatment sequentially, after sedimentation
is filtration. Filtration is a process which arguably can be considered a
physical process as well as biological process. It is because of its
biological aspect that it attracted a sub-heading as seen above, otherwise
it should come after sedimentation under physical principles. According
to WAHEB (1991), filtration is a process of water treatment which
makes the appearance of water attractive, reduces pathogenic bacteria
and removes protozoan cysts. Various devices are used for filtration:
thick white linen cloth (the trek filter) which may remove large particles
including Cyclops –the intermediate host of Guinea worm from water.
Others include the two types of sand filter - the slow sand filter and the
rapid sand filter. We equally have house hold filter, domestic filter etc.
A slow sand filter consists of a large tank with a bed through which
water filters to a set of drains which lead the filtered water to an outlet
chamber. The filter work through series of straining processes. As
filtration progresses the sand grains is the top layers of the bed becomes
coated with sticky deposition in which bacteria and algae multiply.
According to Godman and Gutteridge (1979), numerous small plant
bodies (algae) grow on top of the layer of sand and form slime on the
surface. These plant bodies feed on bacteria in the water and act as a
true filter for bacteria. A filter bed with a proper growth of slime is
called a “ripe” bed, and water that passes through a filter bed should not
be used unless the bed is ripe. After a time, the slime becomes too
compact to allow water to pass through and then it is scraped off and a
new layer of slime grown in its place. This takes about two days. It is
because of the action of the algae (plant bodies) that feed on bacteria
(contaminants of water) thus de-germing same that this process is
considered a biological process. The passage of the filtrate down the
layer for another process is a physical process, thus the arguments above
hold.
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189
Fig. 1.2: Network of Water Treatment Activities
Source: (Godman and Gutteridge, 1979)
3.3.3 Chemical Principles involved in Water Treatment
Chlorination: In water treatment plant, after filtration comes
chlorination and this is the final stage of the process. In the chlorinating
plant, water is mixed with small quantities of chlorine, a gas which will
readily kill any remaining bacteria. Other chemicals that can be used
outside chlorine include ozone, iodine, Milton and potassium
permanganate (WAHEB, 1991).
The strong oxidising properties of chlorine are used to break down the
organic decomposing compounds into either tasteless or unstable
volatile substances that may be absorbed by activated carbon or
dissipated to the atmosphere. The chlorine added to water is intended to
kill pathogenic organisms, maintain a free residual concentration of at
least 0.5 ppm (part per minute) and to safeguard the water up to the
point of consumption. Chlorine dosage normally varies with the degree
of pollution of water and the minerals or gasses present in the water. It
should be enough not only to meet the normal “chlorine need” of the
water but also to maintain a detectable “chlorine residual” of 0.5 ppm at
the furthest point of water collection. During epidemics of waterborne
diseases, super-chlorination may be practiced.
Chlorine used as free chlorine or as hypochloride acts as a potent
oxidising agent and so dissipates (wastes or expands) itself to the side so
rapidly until amount in excess of the chlorine demand has been added.
Acid which dissociate very easily and poorly is formed.
N.B: It is the hypochlorous acid (HOCl) formed that kills the germs.
Hypochlorites are used largely in the form of present day high
taste calcium hypochlorites (Ca(HOCl)2. Their ionisation pattern is as
follows:
Ca (HOCl)2 +H20 Ca2 + +H20 + 2OCl -
+ H2 (g)
OCl H+ HOCl (hypochlorite acid)
The ion (hypochlorites ion) then establishes equilibrium with hydrogen
ion in the water to form other batches of hypochlorites acid. It should be
noted however that chlorine tends to decrease the pH whereas
hypochlorites tends to increase it.
Reactions with impurities in water to be disinfected
190
Chlorine and hypochlorite acid react with a wide variation of impurities
in water, including ammonia (NH3) which is, a product of nitrogenous
organic matters in the water. When NH3 reacts with HOCl, the
following reactions occur.
1. NH3 + H + OCl NH2Cl + H20 – (1) Monochloride
2. NH3 + 2H+OCl NHCl2 + 2OH – (II) dichloride
3. NH3 + 3H+ OCCl NCl3 + 3 OH - (III) Trichloride
The monochloride and dichloride have significant disinfecting power
and should be taken into consideration when accessing the chlorine
residual of water. At this point, the question concerns the significance of
chlorine residual with regards to potable water disinfection.
Disinfection is a process designed to kill harmful bacteria or
microorganism in water and not necessarily a production of sterile
water. In disinfecting water with these, two important parts must be
considered:
(a) the time of contact between these and water (contact period )
(b) the concentration of the disinfecting agent
The expression could be represented mathematically thus: Kill = CXT
(kill varies with concentration (C) multiply by time (T) or Kill = KCT
(where K is a constant)
The same thing holds for the use of hypochlorite for disinfecting potable
water.
To effect the desired result; concentration of chlorine (Cl2) or
hypochlorite (HOCl) should be such that the demands for all the
impurities in the water is satisfied and enough of them remain (free
Cl2).
Expressed graphically we have this
Total Cl2 demand = (free Cl2 residual) + (combined Cl2 residual)
Combined Chlorine (Cl2) Residual: By combined Cl2 residual we
mean the quantity of Cl2 being a portion of the initial Cl2 impact that
went into reaction with organic and inorganic impurities in the water as
the portion of the chloramines (NH2Cl) which was utilised for the killing
of germs in the water.
Total Cl2 demand = free Cl2 residual + combined Cl2 residual.
EHS 304 MODULE 3
191
Free chlorine (Cl2) residual: By this we mean the left over quantity
from Cl2 being a portion of the Cl2 impact that went into reaction with
the organic and inorganic impurities in the water as well as the portion
of Cl2 residual which goes to ensure the chain reaction of disinfection of
water until the final use or consumption of water after supply.
4.0 CONCLUSION
In order to ensure that clean and potable water is used by man,
conscious efforts are made to achieve this through water treatment. The
scope of this treatment depends on the quantity of water and the size of
consumers to be supplied. Whereas domestic water treatment can serve
fewer people and smaller quantity of water, but for large communities
the use of water treatment plants where conventional treatment is done
is preferred. This conventional treatment involves physical, biological
and chemical principles as we have seen.
192
5.0 SUMMARY
In this unit we learnt about the need for water treatment.. Some water
may appear clean but in them disease pathogens and poisonous
chemicals may be found. Treating such will make sure that water-related
or waterborne diseases are not spread.
We also learned the levels of water treatment. These levels depend on a
number of factors: quantity of water to be treated, economy of the
people embarking on the treatment, number of users to be supplied and
the source of water to be treated.
6.0 TUTOR-MARKED ASSIGNMENT
Discuss in details the physical, biological and chemical principles
involved in water treatment.
7.0 REFERENCES/FURTHER READING
Cox, C. R. (1969). Operation and Control of Water Treatment Process.
Geneva: WHO.
Ebisike, A. O. et al. (2009). The Sanitarian and his Work. Ibadan:
Jaainchrist Printers.
Ehlers, V. M. & Steel, E. W. (1969). Principle and Rural Sanitation.
New York: John Wiley Publisher.
Fair, G. M. & Geyer, J. C. (1963). Water Supply and Waste Disposal.
(5th
ed.). New York: John Wiley Publisher.
Godman, A. & Gutteridge, A. C. (1979). A New Health Science for
Africa. London: Longman Group Ltd.
Njoku, P. A. (1998). Certificate Health Science and Health Education
for School and Colleges. Onitsha: Africana Educational
Publishers (Nig) Ltd.
Nnaji, E. (1990). “Water Supply and Sanitation.” Unpublished Lecture
at School of Health Technology, Oji River. Enugu state.
Oluwande, P. A. (1983). A Guide to Tropical Environmental Health and
Engineering. Ibadan, Nigeria: Nigerian Institute of Social and
Economic Research.
EHS 304 MODULE 3
193
West Africa Health Examination Board (WAHEB) (1991). Water and
Building Sanitation. Ibadan: Sterling Publisher Ltd.
Wilkie, W. (1965). Jordan’s Tropical Hygiene and Sanitation. (4th
ed.).
United Kingdom: Bullsie Tundal and Company.
194
UNIT 2 PUBLIC HEALTH IMPORTANCE OF WATER
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Physical, Chemical and Biological Characteristics Quality
Water Supply
3.1.1 Physical Characteristics
3.1.2 Chemical Characteristics
3.1.3 Biological Characteristics
3.2 Basic Classification of Water Related Disease
3.3 Concept of the Faecal-Oral Route of Disease Transmission
and the Classic Waterborne Disease Cycle
3.4 Effect of Improvement of Water Supply on Public Health
3.5 Use of Water
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/Further Reading
1.0 INTRODUCTION
The essence of water treatment is to supply wholesome water to the
public as seen in the last unit. Water has much profound influences on
human’s health. At a very basic level, a minimum amount of water is
required for consumption on a daily basis for survival and therefore
access to some form of water is essential for life. However, water has
much broader influences on health and well-being and issues such as the
quantity and quality of the water supplied are important in determining
the health of individuals and whole communities. The first priority must
be to provide access for the whole population to some form of improved
water supply. The quality of water does have a great influence on public
health, in particular the micro biological quality of water and so is
important in preventing ill health. Poor microbiological quality is likely
to lead to out breaks of infectious water-related disease.
The public health importance of water explains the role played by water
in the transmission of diseases and other uses which include biological
use, water sanitation especially washing and ablution and water
transport as a means of relaxation (Nnaji, 1990).
EHS 304 MODULE 3
195
2.0 OBJECTIVES
At the end of this unit, you should be able to:
explain the characteristics of good quality water supply
describe the basic classification of water-related disease
describe the concepts of the faecal-oral route of disease
transmission and the classic waterborne disease cycle
enumerate how improvements in water supply will lead to
improvement in health and reduction in morbidity and mortality
rate
discuss the general uses of water to the public.
3.0 MAIN CONTENT
3.1 Physical, Chemical and Biological Characteristics of
Quality Water Supply
When a new water scheme, especially a drilled well is put into use, there
may be complaints from the users about its taste, colour, appearance, or
odour. The colour, turbidity and taste, of water are measures of its
acceptability and or attractiveness to consumers. They do not necessarily
indicate whether or not water is safe (Bruce and Hobson, 1979).
Water that is safe for drinking is called potable. It must have basic
essentials which are normally grouped into the above headings.
3.1.1 Physical Characteristics of Water
(a) Appearance: Potable water should be clear. Water that has
drained through swamps, forest or decaying organic matter may
contain brownish or reddish colour or stained due to organic
acids dissolved fromm decaying leaves, roots and stems of
plants. There are two type of colour- the apparent colour and true
colour. The true colour is that found in water after suspended
particles have been removed. The apparent colour is true colour
plus colour due to suspended particles.
(b) Odour: Good quality water should be odourless. The presence of
decayed organic substances introduce odour in water. Odour
should be absent or very faint for the water to be acceptable.
(c) Taste: Taste in water is caused by algae, excessive organic and
inorganic substances or industrial wastes. Good quality water
should be tasteless.
(d) Turbidity: This is due to the presence of suspended particles or
colloids in water. Turbidity of water is the measure of how much
196
interference is caused to the passage of light through the water.
Turbid water is unattractive to the users, affects filtration and
encases the pathogenic bacteria making it impossible to be killed
by disinfectants. To ensure proper chlorination turbidity must be
removed.
3.1.2 Chemical Characteristics
(i) Hardness: This occurs due to the presence of Calcium and
Magnesium trioxocarbonate (iv) and hydrogen trioxocarbonate
(iv) (carbonate hardness which can be removed by heating) and
calcium sulphate, calcium chloride, magnesium sulphate and
magnesium chloride, (non-carbonate hardness, which cannot be
removed by heating). Hard water does not lather well with soap
because the calcium and magnesium salt precipitate curd from the
soap.
Generally, rain and upland water are soft; rivers range from soft
to hard, while spring and wells are usually hard. Hardness in
water produces fur in kettle and forms scale in boilers. The curd
of hardness adheres to the skin and clings firmly to wash basins.
In cooking, the green of vegetables is discharged and the fibre of
meat toughened. It also causes digestive disorder and less
tolerance may be established over time.
Good quality water therefore needs to be treated. Treatment is
either by heating or treating the water with salts that will displace
the stubborn insoluble salt and make them soluble.
(ii) Chlorides: These are present in most natural waters. A sudden
increase of this salt may indicate pollution by sewage, since
human urine contains about 5,000 mg of chloride per litre (Bruce
and Hobson, 1979). Good quality water should not have this in
excess either by natural factor as above or introduction during
chlorination, during water treatment.
(iii) Iron: Iron in most natural and ground waters may be heavily
charged. The iron of piped water supplies however, is usually
derived from rusted pipes. The quantity of iron in a water sample
should not exceed 0.05 parts per 100.00.
(iv) pH: This is a measure of hydrogen ion concentration and
indicates whether water is acidic (pH below 7), neutral (pH 7),
alkaline (pH above7) . In conjunction with alkalinity (caused by
hydroxides, carbonates and bicarbonates), carbon dioxide and
EHS 304 MODULE 3
197
other constituents, the pH value serves to indicate whether water
is likely to be corrosive or scale forming.
(v) Dissolved oxygen: Oxygen dissolved in water used by aerobic
bacteria to oxides organic matter, and is especially significant in
rivers receiving discharged sewage or other organic effluent.
Heavily polluted waters may become devoid of oxygen and
hence offensive through the release of hydrogen sulphide.
(vi) Absence of poisonous substances: Good quality water should
not contain either natural or artificial poisonous substances e.g.
nitrates or the fluorides (Oluwande, 1983).
3.1.3 Biological Characteristics
Under this, we have the macroscopic and microscopic levels of
pollution/contamination. Macroscopic and nuisance organism, larvae,
crustacean and large number of algae or filamentous should not be
allowed in drinking water.
Bacteriological Characteristics
Drinking water must not contain disease causing organisms. These
organisms may be:
bacteria e.g. cholera and typhoid organism etc.
protozoa e.g. amoebic dysentery
viruses e.g. infectious hepatitis
worms e.g. guinea worm infection
fungi, e.g. ringworm of the foot etc.
World Health Organisation (WHO) guidelines and most natural drinking
water standards take the presence of Escherichia coli (E. coli) or thermo-
tolerant coliforms as an indication of recent faecal pollution from human
or warm-blooded animals (WHO, 1993). Thus, the WHO guideline
value of zero E. coli or thermo-tolerant coliform bacteria in any 100ml
sample of drinking water was established because even low level of
faecal contamination may potentially contain pathogens.
Given this clear and unambiguous guidelines, it is reasonable to
conclude that drinking water exhibiting faecal contamination at any
point in the distribution to consumption sequence should give cause for
concern.
198
SELF-ASSESSMENT EXERCISE
In consideration of all the foregoing, do you think that good quality
water is readily available for peoples use?
3.2 Basic Classification of Water Related Diseases
Under this section we are to see some diseases whose occurrence is
water related. By their presence, the answer to the question above is
given to mean that good quality water is scarce and the presence of
contaminated water is rampart, hence the existence of water-related
diseases.
Below is a table of four water-related transmission mechanisms.
Table 2.1: Environmental Classification of Water-Related Infections
S/N Category Infection Pathogenic Agent
1. Faeco-oral
Water-borne or
Water
wash
Diarrhoeas and
dysenteries
Ameobic Dysentery
Balantidiasis
Compilovater enteristis
Cholera
E. Coli Diarrhoea
Giardiasis
Rotavirus Diarrhoea
Shigellosis (Bacillary
Dysentery)
Versiniosis
Enterio fever
Typhoid
Paratyphoid
Poliomyelitis
Hepatitis A
Leptospirosis
Ascariasis
Trichuriasis
Protozoa
P ,,
Bacteria
B ,,
B ,,
Protozoa
Virus
B Bacteria
B ,,
B ,,
B ,,
B ,,
Virus
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199
Source: Adopted from WAHEB (1991)
Another classification is equally given below. It has additional
information, which centered on the route through which the disease
pathogen enters and leaves the body of a person.
2
a)
b)
Water wash
Skin and Eyes
Infection
Others
Infectious Eye diseases
Infectious Eye diseases
Louse-Borne typhus
Louse-Borne Relepsing
fever
Miscellaneous
M ,,
Rickettsa
Spirochaete
3
(a)
(b)
Water Based
Penetrating skin
ingested
Schistosomiasis
Guinea worn
Chlonorchiasis
Diphylobothriasis
Fasciolopsiasis
Paragonimiasis
Others
Helminthes
H ”
H ”
H ”
H ”
H ”
H ”
4 Water related
insect vector
a)
b)
Biting near water
Breeding in water
Onchocerciasis
(Filariasis)
Sleeping Sickness
Filariasis
Malaria
River Blindness
Mosquito-Borne
Viruses
Yellow fever
Dengue
Other
Helminthes
Protozoa
Helminthes
Protozoa
Helminthes
Virus
Virus
Virus
200
Table 2.2: Diseases Related to Water and Sanitation
Group
Disease Route
leaving the
host
Route of
infection
Diseases which
are
often water
borne
cholera
Typhoid
Infections hepatitis
Gardiasis
Amoebas
Dracunculiasis
Faeces
Faeces/Urine
Faeces
Faeces
Faeces
cutaneous
Oral
Oral
Oral
Oral
Oral
Percutaneous
Diseases which
are
often
association with
poor hygiene
Basically dysentery
Enteroviral diarrhoea
Paratyphoid fever
pinworm (enterobius)
Amoebiasis
Scabies
Skin sepsis
Lice and typus
Trachoma
Conjunctivitis
Faeces
Faeces
Faeces
Faeces
Faeces
Cutaneous
Cutaneous
Bite
Cutaneous
cutaneous
Oral
Oral
Oral
Oral
Oral
Cutaneous
Cutaneous
Bite
Cutaneous
Cutaneous
Disease which
are often related
to inadequate
sanitation
Ascariasis
Trichuriasis
Hook worm
(Ancylostoma/Necator)
Faecal
Faecal
faecal
Oral
Oral
Oral
Percutaneous
Diseases which
are life cycle of
parasite in water
Schistosomiasis
Urine/faeces Percutaneous
Diseases with
vectors passing
part of their life
cycle in water
Drancunculiasis
cutaneous
Percutaneous
Source: Adapted from Bradloy, D. J, London, School of Hygiene and
Tropical Medicine
SELF-ASSESSMENT EXERCISE
Close your book and reproduce any of the tables above.
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3.3 Concept of the Faeco-Oral Route of Disease
Transmission and the Classic Waterborne Disease Cycle
Faeco-oral transmission occurs mostly through unapparent faecal
contamination of food, water and hands - the three main items which
regularly make contact with the mouth. See figure 8 below.
Fig. 2.3: Pathways of Faeco-Oral Transmission
Source: Lucas and Gilles (1984)
It should be noted that minute quantities of faeces can carry the infective
dose of pathogens. Thus, dangerously polluted water may appear
sparkling clear, contaminated food may be free of objectionable odour
or taste and apparently clean hands may carry and transmit disease.
As shown in the diagram, food occupies a central and important
position. Not only can it be contaminated directly by faeces but also
indirectly through polluted dirty hands, contaminated soil and filth flies.
Water may be polluted directly by faeces or faeca material may be
washed in from the polluted soil on the river bank. From the diagram,
contamination can be equally done by the soil or flies (example, fruits
and vegetables from our gardens and direct contact between the flies
that have touched faeces with our food respectively).
The above diagram can be represented in another form when water
alone is considered. This is shown in the diagram below which shows
the classical waterborne infection cycle.
Flies
Food
Mouth
Hand
Water
Faeces
Soil
202
Fig. 2.4: A Classical Water-borne Infection Cycle
Source – Tebbutt T. H. Y, 1992
3.4 Effects of improvement of Water Supply in Public Health
It is pointless asking if the improvement of the quality of water supplied
to the public will be of any effect. This is because the answer is in the
affirmative. It will have positive effect in the reduction of diseases that
are waterborne or water related. People will no more have high
morbidity and mortality due to such diseases. Also the money, time and
energy that are wasted in hospital treating people will be minimally
reduced.
In line with the above, the table below shows the potential reductions in
morbidity for different diseases as a result of improvements in water
supply and sanitation.
Table 2.1: Potential Reductions in Morbidity for Different Diseases
as a Result of Improvements in Water Supply and Sanitation
Diseases Projected reduction in
morbidity (% )
Cholera, Typhoid 80-100
Diarrhoeal diseases dysentery,
gastroenteritis
40-50
Dracunculiasis 100
Schistosomiasis 60-70
Source: World Health Report (1995)
Pathogens in
excreta Contaminated
Water source
Infected
person
person Susceptible
Consumption of
Contaminated water
source
ater source
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3.5 Uses of Water
a) Domestic use:
drinking and cooking
bathing
washing
scrubbing
b) Comfort requirement: domestic air conditioning
c) Agricultural use:
water for crop irrigation
livestock requirement
d) Industrial use:
cooling
washing
power generation
transportation
fire fighting and street cleansing
steam generation
raw material.
4.0 CONCLUSION
Water is an indispensable gift God blessed man with. Its full use and
benefit should be maximally harnessed if there are no pollution and
contamination by disease causing organisms whose presence has caused
man to be conscious and use it with caution to avoid getting one disease
or the other from same. We therefore need to strive to get quality water,
I, thus join UN conference at Mardel Plata (1977) to say, that, “All
people, whatever their stage of development and social and economic
condition have the right to have access to drinking water in quantities
and of a quality equal to their basic needs”.
5.0 SUMMARY
In this unit, we learned that good quality water should be such that have
its physical, chemical and biological characteristics not in doubt, that is,
that should not by their composition injure man as he uses it.
Waterborne diseases abound with their different vectors. A
diagrammatic representation of faeco-oral route of transmission was
equally given and in it we saw that water is as necessary as food in the
transmission of faeco-oral infections.
204
There will be reduction of diseases if there is conscious effort by the
public to embark on good water supply and proper sanitation.
6.0 TUTOR-MARKED ASSIGNMENT
Discuss water and public health in the following context:
1. Physical and chemical characteristics only
2. Environmental clarification of water related diseases or
infection.
7.0 REFERENCES/ FURTHER REACHING
Anon, Report of a National Water Quality Seminar, Romania, WHO-
EURO, Rome, 1995.
Ashiru, R. O. (2007). “Public Health Laws and Pollution.” In: 2007
Mandatory Continuous Education Programme (MCEP) Lecture
Notes, for Environmental Health Officers Registration Council of
Nigeria at
Filbon Quest House New Haven, Enugu.
Bruce, F. E. & Hobson, W. (1979) The Theory and Practice of Public
Health, Water Supply, Sanitation and Disposal and Waste
Matter, 9, 130 131.
Lucas, A. O & Gilles, H. M. (1984). A Short Textbook of Preventive
Medicine for the Tropics. London: Hodder and Stoughton.
Nnaji, E. (1990). “Water Supply and Sanitation.” An unpublished
Lecture at school of Health Technology Oji River, Enugu State.
Oluwarde, P. A. (1983). A Guide to Tropical Environmental Health and
Engineering. Niger. Nigeria.
Treveth, A. F. Carter, R C. & Tyrrel, S.F. (2005). “The importance of
Domestic Water Quality Management in the Context of Faecal-
Oral Transmission.” Journal of Water and Health.
West Africa Health Examination Board (1991). Water and Building
Sanitation. Ibadan: Sterling Publishers Ltd.
World Health Organisation (1993). Guidelines for Drinking Water
Quality Recommendations.
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UNIT 3 URBAN AND COMMUNITY STORM WATER
MANAGEMENT
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Meaning of Storm Water and its Generation
3.1.1 The Need for Storm Water Management
3.2 Storm Water Management
3.2.1 Structural Storm Water Management Strategies
3.2.2 Non-Structural Storm Water Management
Strategies
3.2.3 Institutional Arrangement and Participation in
Urban Storm Water Management
3.3 Constraints to Storm Water Management
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References /Further Reading
1.0 INTRODUCTION
From previous units, you are aware of the hydrological cycle. . When it
rains, part of the water will percolate into the soil, part will evaporate
back into the atmosphere while the excess will run on surfaces until it
finds where to join such as water bodies like rivers, lakes etc. It is this
quantity that runs on surfaces that we may refer to as storm water. The
task in this section is its management precisely, the topic is urban and
community storm water management.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
discuss storm water and its generation processes
explain the need for storm water management
discuss storm water management and its processes
enumerate the constraints to storm water management.
206
3.0 MAIN CONTENT
3.1 Meaning of Storm Water and its Generation
By way of definition storm water is that quantity of water usually during
rainfall or immediately after which remains on top of the ground after
the ground must have been satiated with water or as a result of
impervious ground which normally flows horizontally overland
downhill.
The rate or amount of storm water formed depends on the amount or
quantity and frequency of rainfall, the nature of the soil or land surface,
the topography and the timing of the rainfall.
Urbanisation, the conversion of forests and agricultural land to sub-
urban and urban areas is proceeding at an alarming and unprecedented
pace in most places due to population explosion and quest for alternative
land uses. Storm water discharges have emerged as a problem because
the flow of water is dramatically altered as land is urbanised. With
urbanisation, storm water generation is higher or faster. Typically,
vegetation and top soil are removed to make way for buildings, roads
and other infrastructures and drainage networks are installed. According
to Emerson (2003), the loss of water retaining functions of soil and
vegetation causes storm water to reach streams in short concentrated
bursts. According to Claire (undated) road networks, parking lots, and
other impervious surfaces cause generation of storm water faster and
hasten the flow of water to streams where available.
More so, due to vast networks of underground pipes and utility conduits
underlying urban areas, percolation of rainwater becomes difficult.
Surface water runoff (storm water) easily forms and this usually poses
danger to the occupiers of such places if not properly handled.
3.1.1 The Need for Storm Water Management
The need for storm water management arises because of the problem it
causes to humanity. According to National Academy of Science
(retrieved 13-08-12), storm water has long been regarded as a major
culprit in urban flooding. However, only in the last 30 years have policy
makers appreciated its significant role in degrading the streams, rivers,
lakes and other water bodies in urban and suburban areas. Large volume
of rapidly moving storm water can harm species habitat and pollute
sensitive drinking water sources, among other impacts. Urban storm
water is estimated to be primary source of impairment for 13 percent of
assessed rivers, 18 percent of lake and 32 percent of estuaries -
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significant numbers given that urban areas cover only 3 percent of the
land mass of the United States (National Academies of Science,2008).
Storm water encourages flooding which can cause some physical
impacts like the widespread disruption to transportation, power and
communication system as well as structural damage to buildings and
infrastructure. The disruption, damage to properties, loss of possessions
as well as financial worries and other stresses from living in damp
houses mean that flood event can place a considerable strain on
households (Parkinson, 2003). These factors are recognised to be
significant even in countries such as the United Kingdom whose
flooding is typically small-scale, short-lived and shallow (Tapsell,
1999). However, those factors take on extra dimension in cities in
tropical regions. According to UN-HABITAT (2003), it is the poor who
are most susceptible and consequently suffer the most.
The environmental health impact of storm water flooding comes next.
There is considerable empirical evidence to indicate that flooding and
poor drainage have a significant impact on the prevalence of illness, and
that large-scale flooding may disrupt water supply and sanitation system
and result in diseases epidemics (UN-HABITAT, 2003). In poorly
drained areas, with inadequate sanitation, urban runoff mixes with
excreta, spreading pathogens around communities and increasing risks
to health from various waterborne diseases. In areas where storm water
accumulate either in blocked drain or depressed areas, mosquito
breeding will be encouraged with its deleterious effects on the society.
There are also impacts of flooding on the urban and poor communities.
The poor have fewer resources available for rebuilding and they
generally receive little external support to recover from flooding
(Napier, at al. 2002). Their livelihoods are more vulnerable to the risks
associated with flooding and are more susceptible to disruption. The
location of poor neighbourhoods and the inferior construction materials
used to build homes for the poor contribute to their greater vulnerability
(Francis, 2000). Damage to homes caused by flooding places extra
demands on the limited resources of the poor. More so, there could also
be loss of working days required to repair structural damage or the
increased prevalence of illness, causing families to redirect assets
towards treatment.
With all the above problems, the best is to manage storm water well so
that it no longer poses problems to the society.
3.2 Storm Management
In order for urban and community authorities to address the diverse
problems related to flooding described above and the complexities of
208
urban environmental management, it is important that they adopt some
strategic approaches towards the development and implementation of
storm water management plans. Against this background, there are some
strategic approaches to urban and community storm water management.
According to Parkinson (2003), a combination of structural and non-
structural storm water management strategies are considered to be
complementary aspects of a comprehensive and integrated storm water
management strategy.
3.2.1 Structural Storm Water Management Strategies
Structural storm water management strategies focus on physical
intervention and investments in engineered infrastructure for improved
drainage. According to Claire (undated), storm water management
regulations often require reduction of peak flow rates by routing flows
to a “detention basin” designed for this purpose. According to him, a
detention basin or pond is the most commonly used (best management
practice (BMP)) to control runoff and nonpoint source pollution.
Structural storm water control measures are designed to reduce the
volume and pollutants of small storms by the capture and reuse of storm
water, the infiltration of storm water into porous surface and the
evaporation of storm water. Example include rainwater harvesting
system that capture runoff from roofs in rain barrels, tanks or cisterns,
the use of permeable pavements, the creation of “infiltration trenches,”
into which storm water, can seep or is piped, the planting of rain gardens
on both public and private lands and the planting of ‘swales’ along the
roadside that capture and treat storm water. Holman-Dodds et al. (2003),
called the above structural approach “Low-Impact Development” (LID)
technologies. These LID technologies, e.g. use of green roofs, cisterns,
rain gardens, on-site infiltration ponds, etc can have a significant impact
on the urban water cycle by increasing on site recharge and reduce
runoff rates.
3.2.2 Non-Structural Storm water Management Strategies
Non-structural storm water management strategies for mitigation of
flooding impacts focus upon preventive action and rely predominantly
on behavioural changes in order to be effective. These are particularly
relevant in low-income communities in tropical climates where flooding
is inevitable and resources for infrastructure are scarce. Faisal et al.
(1999) concluded that a well coordinated and balanced combination of
both structural and non-structural measures is required as part of the
long-term flood mitigation strategies. Example of different types of non-
EHS 304 MODULE 3
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structural storm water management strategies are summarised in Table
3.1 below.
Table 3.1: Non-Structural Strategies for Flood Control and
Mitigation of Environmental Health Problems
Flood avoidance Preventive responses which aim to ensure that flood
problem are avoided.
Flood
Mitigation
Immediate responses to flood warnings before a
flood, and the courses of action to take during a flood
to reduce risks.
Flood Recovery
Actions to be taken after a flood event to enable
communities to recover from the impacts of a flood
system
Source: Faisal et al. (1999)
The above is a resume of non-structural strategies for flood prevention
and management. Below are efforts made at adding flesh to the table.
(a) Flood prevention strategies: Flood avoidance or prevention
strategies are precautionary interventions that involve structural
adaptations or constructions to reduce the impacts of inundation,
or the relocation of houses that are on drainage pathways and
flood plains. Relocation is an option where the government that
be or the community affected can withstand the financial burden
of doing so. Against this, Tucci (2002), notes that experience
indicates that large scale eviction and forced relocation can
exacerbate (worsen) social problems which can be more
problematic for urban authorities than the original problem. As
demand for land in cities is high, it is not possible to assign land
purely for flood management purpose; it therefore needs to have
an alternative use to ensure that informal settlement does not
appear. Where resettlement is the only viable option, it will be
Solid Waste
Management
Control of solid wastes to avoid blockages and
reduction in hydraulic capacity of the drainage
system
Pollution
mitigation
Reduction in the discharge of pollutants into the
storm water
drainage system.
Vector control Improved practices to reduce vector transmission of
disease related to urban drainage and flooding.
210
necessary to ensure that resettlement plans are designed and
implemented with the groups that are being resettled and
infrastructures that will serve them provided as well (Santosa,
2003).
(b) Flood mitigation strategies: This involves responses both before
and during a flood event, which include advance warnings, the
operation of flood control works and emergency unblocking of
blocked inlets and drains. An important aspect is the
identification of potential events and communication is critical to
ensure that mobilisation and evacuation responses strategies are
effective. Also important is the necessity to consider the choice
of evacuation routes. Of particular importance is the fact that
poor communities often have already developed informal but
sophisticated coping strategies, which may originally have
developed in rural communities (Sware, 1982). Local perceptions
of flood warnings and existing coping strategies should be
understood and taken into account in the design of intervention
which aims to reduce the effect of flooding.
(c) Flood recovery strategies: Post flood recovery strategies aim to
enable communities to respond effectively to the consequences of
flood and to permit local and central authorities to organise and
coordinate relief activities, including making the best use of local
resource, and properly managing national and international relief
assistance. Medium and long-term interventions may be needed
to support population affected by flooding (WHO, 2002).
Post flood recovery involves numerous activities in relation to the return
to normal life including evaluation of damages, rehabilitation of
damaged properties and the provision of flood assistance to flood
victims.
Concerning the environmental health problems caused by storm water
and drainage problems, there are some non-structural strategies for their
mitigation. Below are some of them:
(i) Pollution mitigation and solid waste management: Problems
related to poor drainage are worsened by poor solid waste
management as uncollected solid waste often enter surface drains
and sewers causing blockages and reduced flow capacity.
Flooding is more likely to occur if solid wastes accumulate in
drains, and blocked drains create insect breeding sites, thus
encouraging disease transmission.
Structure elements such as the incorporation of solid waste traps are
important design aspects of drainage system (Armitage and Rooseboom,
EHS 304 MODULE 3
211
2000). However, non-structural solid waste management strategies may
reduce the need for extensive cleaning of storm water drainage systems
prior to the onset of the flood season. These strategies should promote
awareness of the impacts of solid waste in relation to the flooding and
health hazards associated with blocked drain.
Similarly pollution form storm water runoff may be reduced by the
introduction of non-structural strategies aimed at limiting the ingress of
pollutants into the drainage system, especially from construction site and
industrial sites. Attempts to control pollutants from storm water drainage
systems include a range of practices such as efforts to inform residents
of the polluting effects of improper disposal of pollutants into surface
drains and the provision of collection services for toxic chemical
(Taylor, 2002).
(ii) Control of disease vector: Non-structural strategies relevant to
storm water management which focus on improved
environmental health are particularly important in relation to the
control of mosquito-breeding sites. Drainage of runoff by
controlling surface water and water logging and by eliminating
unnecessary open water surfaces is an essential and effective tool
for reducing and eliminating mosquito-breeding site. Poorly
maintained drainage canals can provide potential breeding sites
for various mosquito species if they are permanently flooded and
aquatic weeds are not cleared.
3.2.3 Institutional Arrangement and Participation in Urban
Storm water Management
A key element for the successful implementation of non-structural storm
water management programmes is an inclusive approach, which
promotes participation of stakeholders in the development and
implementation of urban drainage plans (Affeltranger, 2001). In this
section, the importance of participation in non-structural storm water
management programmes is stressed and these are discussed in relation
to the partnership and institutional arrangements for management and
implementation.
Public participation is an opportunity for urban authorities to assess the
social feasibility of storm water systems and flood response strategies.
Experiences from high-income countries such as the United States
demonstrate that urban runoff control programme needs public backing
and involvement to succeed. A strong motivation to act is essential to
the success of storm water management projects. From the above, it
means that urban drainage system cannot be designed in isolation from
212
the community they serve. Those responsible for urban storm water
management should enlist the support of local officials prior to any
initiative to implementation and should engage with the public, building
on local knowledge and resources, working with local social
organisations and management system, and using participatory methods
for planning, implementation, monitoring and evaluation.
From the above it means that the public or community where these
services are rendered should be involved in:
(i) Planning: A considerable amount of physical data is required but
these data may be scarce and difficult to get if the benefiting
community is not involved.
(ii) Implementation: Generally, squatter upgrading cannot be
achieved without the participation of the benefiting communities
especially where people’s lives will be disrupted by removal,
reflection and partial demolition of their homes. Their consensus
and collaboration are all needed.
(iii) Operation and maintenance: Users need to be aware of operation
and maintenance requirements at the neighbourhood level. Often,
one of the best solutions for maintenance is for community
members to be responsible for the management of the drainage
system and even storm water management as the regular
inspection and cleaning of drains is an important task that can be
performed without specialised skills.
3.3 Constraints to Storm Water Management
Implementation
Some constraints affect the smooth running or achievement of all that
have been said above. They are the following:
(i) Institutional responsibility for urban drainage is often narrow.
There are many institutions as there are many responsibilities
over public utilities and clear demarcation of boundaries is a
problem. For instance, public utilities or water companies may
have the responsibility for sewerage whereas road drainage is
often the responsibility of local authority or environmental
agency.
Therefore the overall planning needs to be considered in relation to land
use in urban and semi-urban area and in particular those communities
who inhabit this land.
(ii) The design and implementation of disaster mitigation at the local
level such as that associated with flooding is a complex task for
EHS 304 MODULE 3
213
urban authorities particularly as they have to cope with very
complex stakeholders.. These stakeholders have different
perceptions and relationships to natural hazards, a reflection of
different socioeconomic and socio-psychological backgrounds.
(ii) Non-structural approaches to storm water management can work
well provided the municipal authorities are receptive to the
involvement of community groups in project implementation.
Collaboration between government agencies and non-
governmental organisation, in conjunction with communities is
essential but often challenging. Many of these constraints may be
overcome if there is a political and institutional commitment to
overcoming problems and specifically a consideration of and
concern with the needs of the urban poor.
4.0 CONCLUSION
From all the foregoing, we can conclude by saying that due to changes
that occur on the surfaces of land as a result of urbanisation and human
activities, storm water formation is not scarce in most communities and
urban areas. To cope with it and avoid the problems it breeds, deliberate
and conscious efforts are made towards managing same. These normally
come in form of structural and non-structural management strategies,
which if well applied, will see man through these hurdles.
5.0 SUMMARY
In this section we have been able to give the definition of storm water
and how it is generated. Its generation is caused mainly by the
compaction and hardening of the top soil making percolation
impossible.
We also dealt with the need for storm water management which mainly
centered on prevention of physical and health problem that would have
arisen if not well managed. More so, the management strategies which
centre on structural and non-structural approaches were discussed.
Finally the constraints to storm water management implementation were
discussed. If the constraints were tackled well, success stories would be
told.
6.0 TUTOR-MARKED ASSIGNMENT
1. Write on the following:
(a) Define storm water.
(b) Explain factors that facilitate storm water generations.
214
(c) Enumerate the needs for its management.
2 List two approaches to storm water management and explain any
of them.
7.0 REFERENCES/FURTHER READING
Affeltranger, B. (2001). “Public Participation in the Design of Local
Strategies for Flood Mitigation and control.” Technical
documents in Hydrology, 48. Paris: International Hydrological
Programme, UNESCO.
Armitage, N. P. & Rooseboom, A. (2000). “The Removal of Urban
Litter from Storm Water Conduits and streams. Paper 1- The
Quantities Involved and Catchments Litter Management Option.”
Water SA. Vol. 26, No 2, April
Claire Welty (n.d.). The Urban Water Budget. htt://Flakes.org/book
/WATER-ENV-CITY/ Fultext (16). pdf
Emerson, C. H. (2003). “Evaluation of the Additive Effects of Storm
water Detention Basins at the Watershed Scale.” M.Sc. Thesis,
Department of Civil Architectural and Environmental
Engineering, Drexel University, Philadelphia, P.A.
Faisal, I. M, Kabir, M..R. & Nishat, A. (1999). “Non-Structural Flood
Mitigation Measures for Dhaka City.” Urban Water, Vol.1, No. 2
p. 112.
Francis, J. (2000). “Implications of Gender in Floods, Gender and Water
Alliance, November.” http://www.Gender and
wateralliance.org/reports/discussion_ paper_ on_gender and
floods by JF.doc.
Holman, D J. K. et al. (2003). “Evaluation of Hydrologic Benefits of
Infiltration Based upon Storm Water Management.” Journal of
the American Water Resources Association, 39, 205, 215.
Napier, M. L; Ade Bustillos, Santosa, H. & Rubin, M. (2002).
“Understanding the interface between the environment and
sustainable livelihoods in the integration of informal settlement in
Asia, Latin America and Africa: a review of current thinking and
practice.” CSIR Building and Construction Technology, Pretoria,
South Africa, March 2003 http://www.csir.co.za/akani
National Academy of Sciences (2008). Retrieved 13-08-2012.
EHS 304 MODULE 3
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Parkinson, J. (2003). “Drainage and Storm water Management
Strategies for Low-Income Urban Communities.” Environment
and Urbanisation. Vol. 16, No 2, Oct. Retrieved from
eau.sagepub.com on August 13, 2012.
Santosa, H. (2003). “Environmental Hazards Management in Informal
Settlements to Achieve Sustainable Livelihoods of the Poor: the
case of East Java, Indonesia, CSIR Building and Construction
Technology.” Pretoria, South Africa, March 2003
http://www.csir.co.29/akani
Schware, R. (1982). “Official and Folk Flood Warning Systems: an
Assessment” Journal of Environmental Management. Vol . 6,
No 3, pp. 209-216.
Tapsell, S. (1999). “The Health Effects f Floods - The Easter 1998
Floods in England.” Article Series Vol. 3, No 99, U. K.: Flood
Hazard Research Centre, Middlesex, University.
Taylor, A. (2002). “Non Structural Storm Water Quality Best
Management Practices-Monitoring and Evaluation Guidelines.”
Cooperative Research Centre for Catchment Hydrology Working
Document 02/6, Monash University Australia.
Tucci, C.E.M. (2002). “Urban Drainage Management.” In: C.E.M
Tucci. Urban drainage in the humid tropics. UNESCO
International Hydrological Programme (IHP-V), Technical
Documents in Hydrology, No 40, vol. 1, UNESCO, Paris. pp
157-176.
UN-HABITAT (2003). Water and Saintation in the World’s Cities -
Local Action for Global Goals, published in association with
United Nations Human Settlement Programme. (UN-HABITAT),
Earthscan, London, UK.
World Health Organisation (2002). “Flooding: Health Effects and
Preventive Measures.” WHO fact sheet 05/02, Copenhagen and
Rome, 13 September.
216
UNIT 4 DRAINAGE LAYOUT
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Meaning and Concepts of Drainage Layout
3.1.1 Definitions and Insight into some Key Terms Used
in Drainage System
3.2 Wastewater and Storm Water Collection
3.2.1 Conventional Sewerage
3.2.2 Simplified Sewerage
3.2.3 Settled Sewerage
3.2.4 Storm Water Collection
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/Further reading
1.0 INTRODUCTION
Liquid wastes are generated in homes from our kitchens, wash hand
basins, toilets and bath-room, laundry services etc. Also storm water
generated as surface runoff adds to liquid waste and may not be used for
anything domestically. They need to be disposed of too. This section
deals with how liquid wastes are drained and disposed of with emphasis
on their layout pattern.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
discuss the meaning and concepts of drainage layout
explain some key terms used in drainage system
discuss waste water and storm water collections patterns and their
layout.
3.0 MAIN CONTENT
3.1 Meaning and Concepts of Drainage Layout
By way of definition drainage is the process by which water and other
liquids which are not wanted are removed from building premises.
Therefore drainage may be internal or external in every building. The
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internal drainage is that which is situated inside the building and it is
normally constructed by plumbers. The external drainage is that which
is outside the building but within the compound (WAHEB, 1991).The
spatial pattern and arrangement of these networks of pipes both within
and outside the building till the final treatment area of the waste water
and storm water is known as drainage layout.
Drainage system is normally of two parts. The first part is the
continuation of the internal drainage which is normally constructed by
the plumber and the second part consists of the channels into which the
waste water is discharged outside the buildings and this takes different
form with its construction dependent on the form so chosen. If it takes
the form of a sewer to drain into the septic tank, soak away, cesspool or
into main hole of the public sewerage system, it is often build by the
plumbers. However, if it is open drain, it is often built by a bricklayer or
masons.
Fig.4.1: General Features of Building Drainage
Source: (WAHEB, 1991)
1. Fly trap
2. Outside drainage pipe or drain.
3. Water closet flushing tank
4. Water closet (w c)
5. Tee joint
6. Wash hand basin or sink
7. Sink trap or water sink
8. Water closet and water seal
9. Drain pipe for wastewater from the baths and sink etc
218
10. Inspection clamber or manhole
11. Hardcore of ground floor
12. Wall
13. Ceiling
14. Roof
15. Open drain, gutter or flesh drain.
To understand the above sketch and more facts about drainages, some
definitions, explanations and insight into some of the above need be
given.
Water closet (WC): This is made of ceramic or porcelain material with
a unique feature of the water seal. Water seal is always seen inside this
WC which shuts off the house from the remaining part of the water
closet drainage pipe system. It prevents the entry of foul odour into the
building. Water closet can break if subject to rough handing.
Water closet drain pipe: This is the sewer line which conveys waste
water from the water closet to the septic tank or to the public sewer
outside the compound. It is normally 10cm (4’’) for building up to four-
storey high. It may be of asbestos, plaster or metal with plastic and
asbestos. This is very rampant in West Africa. The joint are made up of
different types of pieces like the Tee, the bend and the Y-pieces.
Manhole or inspection chamber: As a rule in sewer lines design and
construction, “manhole” or inspection clambers should be located at
points where the direction, the diameter and the gradient of the sewer
changes. While the inspection chamber is small, manhole is big enough
to allow or accommodate a man to go inside for inspection. The
inspection chamber enables sewer lines to be inspected and cleared of
blocking material.
Wash hand basin or sink: A wash hand basin is different from a sink.
A sink is a special wash hand basin, sinks are normally used for washing
clothes, plates and other house hold materials. They are bigger than
wash hand basins.
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Fig. 4.2: Comparison of a Sink and Wash Hand Basin
Source: WAHEB (1991)
Drain pipes from baths, sinks and wash hand basin: Waste water
from appliances like bath, sinks and wash hand basins are normally
drained away through drains of galvanised pipes. The minimum
diametre recommended is 32 mm (11/4”) for wash hand basins and
38mm (11/2”) for baths.
Fly trap: This is very important for trapping flies and also for
preventing rats, snakes, lizards, and other undesirable creatures from
entering the drain as they may block the drain if allowed to enter.
Open drains: These are employed to drain away rain and runoff water
from the roof and the ground surface of the component. They consist of
channels excavated on the ground surface and lined with concrete,
cement mortar or bricks. They need to be cleaned regularly. In order to
prevent regular blockage by soil waste and sand, they may need
covering with concrete slab which should be removable.
Sub-surface drains: These are of two broad types - the sewers and the
underground drains. The sewers are pipes constructed underground to
convey sewage. The flow is under gravity and ground water infiltration
is not encouraged. Underground drains are pipes with open joints or
other materials used to convey surface runoff which percolates into the
drains. Both sewers and underground drains are illustrated in figure 12.
220
Fig. 4.3: Sub-Surface Drains (a and b)
Source: WAHEB (1991)
According to Wilkie (1965), where a public sewer exists, plans of new
building must show satisfactory provision for the drainage of the
building and connection to the public sewer. Similarly, owners of
existing buildings may be required to provide satisfactory drainage in
connection with their buildings, provided a sewer is available.
3.1.1 Definitions and Insight into some Key Terms Used in
Drainage System
(a) Single pipe system: In this system, all the waste water from the
water closet, the bath, sinks and wash hand basin are discharged
into one drain pipe. Every appliance is provided with suitable
trap which is ventilated to the main drain pipe. The system is
used in multi-storey building. The size of the main drain pipe
must be adequate. A minimum diameter of 15cm is mostly
employed.
(b) One-pipe system: In this system, a separate vent pipe is provided
for the appliances which drain into one main pipe. The system is
also suitable for medium size multi-storey building.
(d) Two-pipe system: In this system, the water closet is drained into
a separate pipe which is ventilated while the other appliances are
drained into another drain pipe which is also ventilated. This
system is suitable for bungalows and up to two-storey building.
This system is particularly suitable for situations where waste
EHS 304 MODULE 3
221
water from the water closet goes into the septic tank and the other
waste water goes into the open drain or soak away.
Fig. 4.4: Common Building Drainage Systems
Source: WAHEB (1991)
(d) Private combined drainage system: This is a system that has
both foul and storm water running through it. As the name
implies it is a privately owned one. The owner of the property is
responsible for the drainage system up to the connection onto the
local authority sewers within the road, so any defects beneath the
footpath and road prior to the connection onto the sewer would
be death with by the home owner.
(e) Private foul and storm drainage system: This system has two
separate systems, one for foul waste and the other for the storm
water. Both system are private to the property and again are the
responsibility of the homeowner up to the connection onto the
local authority sewers within the road.
(f) Private shared drainage system: In this system, two properties
share a system prior to its connection into a local authority sewer.
The two property owners share equal responsibility in term of
maintenance from the junction their drainage system meet up to
the local authority sewer within the road.
(g) Riparian drainage: Riparian ownership applies to rivers,
brooks, streams and any water course that may pass through ones
boundary lines. In some places many water courses have culverts
so that land could be claimed for building work and it is not
222
uncommon for homeowners to have a water course passing
through their property without their knowledge. Where such
obtains, the owner of such place is responsible for its
maintenance up to a level outside his property.
3.2 Wastewater and Storm Water Collection
A sewerage system collects wastewater and can be in the form of
backwater separated from grey water, or mixed with it (sewage). Gravity
is used wherever possible to convey the waste water. It is not surprising
therefore that natural storm water drainage is usually used, because this
is how rainwater runoff is conveyed in nature by gravity. The principle
of using gravity as the driving force for conveying waste water in a
sewerage system should be applied wherever possible, because this will
minimise the cost of pumping. Natural storm water drainage occurs in
what is usually termed a catchment basin. In a catchment basin,
rainwater runoff flows to a common point of discharge, and in so doing,
forms streams and rivers. Crossing a catchment boundary may mean that
the water has to be unnecessarily pumped, requiring an energy source. A
wastewater sewerage system should therefore be within a storm water
catchment basin.
Sewerage systems can be classified into combined sewerage and
separate sewerage. Combined sewerage carries both storm water and
wastewater, while separate sewerage carries storm water or wastewater
separately. Recent trends have been for the development of separate
sewerage systems. The main reason for this is that storm water is
generally less polluted than wastewater, and that treatment of combined
wastewater and storm water is difficult during heavy rain falls, resulting
in untreated overflows (commonly termed combined sewer overflow,
CSO). In practice there is usually ingress of storm water into wastewater
sewerage pipes, because of unsealed pipe joints, and unintentional or
illegal connections of rainwater runoff. Conversely there may be
unintentional or illegal wastewater connections to storm water sewerage.
Wastewater sewerage systems can be classified into three major types:
Conventional sewerage
Simplified sewerage
Settled sewerage
3.2.1 Conventional Sewerage
Conventional sewerage is also termed deep sewerage because the
sewerage pipes are laid deep beneath the ground. Pumping is generally
required at various stages of the sewer pipe network, especially if the
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223
landscape is fairly flat. The larger the population served by the sewerage
system, and the longer the planning horizon is to cope with future
population increases, the larger the diameter of the final pipes. The costs
of the pipes, inspection manholes, pumps and pumping stations and their
construction/installation are therefore high. The costs of operation and
maintenance are correspondingly high because of very conservative
design assumptions.
Source:UNEP.www.unep.or.jp/ietc/publications/freshwater/sb_summary
/index.aspx
3.2.2 Simplified Sewerage
Simplified sewerage is also known as shallow sewerage, reflecting the
shallower placement of the pipes in contrast to the conventional or deep
sewerage. The purpose of simplified sewerage is to reduce the cost of
construction and the corresponding cost of operation and maintenance.
Simplified sewerage design is based on hydraulic theory in the same
manner as for conventional sewerage but has less conservative design
assumptions. Smaller diameter pipes are used when water use per person
is known to be less and the minimum depth of cover of pipes can be as
low as 0.2 m when there is only light traffic. Manholes can be replaced
by inspection cleanouts because of the shallow pipes. The design
planning horizon can be shorter because the population projection may
be uncertain. In a variation of the simplified sewerage, the pipe layout
224
passes through property lots (condominial) rather than on both sides of a
street (conventional). Figures 14 and 15 show the sewerage layouts in
conventional sewerage and in condominial sewerage. The cost of
construction of simplified sewerage can be 30 to 50 percent less than
conventional sewerage depending on local conditions.
Fig. 4.6: Pipe Layout for Condominium Sewerage
Source:UNEP.www.unep.or.jp/ietc/publications/freshwater/sb_summary
/index.aspx
Shallow sewerage is also conducive to local community participation
because sewer pipes have to cross property boundaries. The community
has to agree to this arrangement which extends after construction for
maintenance (e.g. unblocking of sewer pipes). The shallow pipe, and
hence the shallow trenches, also allow members of the community to
participate e.g. by providing labour for digging the trenches. This is in
contrast to conventional sewerage where specialised machinery is
required for the deep trenches.
Simplified sewerage was originally developed in Brazil and is
increasingly being used in other parts of the world. The International
Source Book on Environmentally Sound Technologies for Wastewater
and Storm water Management (hereafter referred to as the Source
Book), published by IWA and IETC provides useful case studies.
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3.2.3 Settled Sewerage
Settled sewerage refers to sewerage for conveying wastewater that has
been settled, for example, in a septic tank. Settled sewerage originated to
convey the overflow from septic tanks where the soil cannot cope or
absorb the overflow. This usually occurs when the groundwater table is
high, or where the soil permeability is low, or where there are rock
outcrops. It can also be used when effluent from septic tanks pollutes
groundwater and it is necessary to convey the effluent off-site and treat
it. Because there are no solids that can potentially sediment in the
sewerage pipes, there is no requirement for the self-cleansing velocity.
Smaller pipes and lower gradients can be used. The cost of settled
sewerage is between a third and a half of conventional sewerage.
Originally developed in South Australia to overcome problems with
failing septic tanks, it has been used quite widely worldwide to upgrade
septic tank systems.
Fig. 4.7: Interceptor Tank in Settled Sewerage
Source:UNEP.www.unep.or.jp/ietc/publications/freshwater/sb_summary
/index.aspx
Where there is no existing septic tank, an interceptor box or tank can be
used. It functions like a septic tank and designed in the same way
(Figure 16). To reduce cost, the wastewater from a group of houses can
be connected to one interceptor tank. Just like in a septic tank, the
accumulation of sludge has to be removed regularly from an interceptor
tank.
3.2.4 Storm Water Collection
Storm water flows through the landscape’s natural drainage system.
Piped storm water collection was a development in European cities to
226
overcome odour and improve aesthetic appearance of wastewater
disposed with storm water. The covering of ditches used for combined
sewerage was an intermediate step in using natural drainage to construct
sewerage for combined wastewater and storm water. Piped sewerage
also allows more land area for road and footpaths. With the separate
collection of wastewater there is an opportunity to return some storm
water flow path to its more natural state to improve urban amenity
value.
4.0 CONCLUSION
From all the foregoing, one can conclude that drainage system in our
home is of importance as it rids our homes of all wastewater generated
by man. Through network of pipes (sewerage system) these wastes are
taken to where nature and man deliberately act on them and make them
less harmful and more useful.
5.0 SUMMARY
In this unit, we have been able to give the meaning and concepts of
drainage systems in our residential environment. In that we saw the
drainage in building both inside and outside and some key term clearly
described for better understanding. Furthermore the types of drainage
systems were equally dealt with just as the different sewerage systems
were also learnt. Some sketches were added to make the points sink.
6.0 TUTOR-MARKED ASSIGNMENT
1. Define drainage layouts.
(a) Explain the following items:
i. Water closet
ii. Sink trap
iii. Manhole
iv. Fly trap.
2. Explain the differences between the following:
i. Single pipe system and two pipe system
ii. Combined drainage system and separate drainage system
3. Write short note on:
i. Conventional sewerage
ii. Riparian drainage
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7.0 REFERENCES/FURTHER READING
Typical Domestic Drainage System Layout Plans – DRAIN
DOMAIN.COM. Draindomain.com/systemlayout.html. Assessed
24/0802012.
Ude, B.C. (2002). ‘Building Services.’ Unpublished lecture delivered at
the Department of Architecture, University of Nigeria, Enugu
Campus.
Ude, B.C. (2003). ‘Water Supply and Drainage.’ Unpublished lecture
delivered at the Department of Architecture, University of
Nigeria, Enugu Campus.
Wastewater and Storm water Collection, in, ‘Environmentally Sound
Technologies in Wastewater Treatment for the Implementation of
UNEP Global Programme of Action (GPA),’ “Guidance on
Municipal Wastewater”. Publisher-UNEP in Collaboration with
Murdoch University Environmental Technology Centre.
West Africa Health Examination (1991). Waste Disposal and
Environment Hazard Control..Ibadan: Sterling Publishing Ltd.
West Africa Health Examination Board (WAHEB) (1991). Water and
Building Sanitation. Ibadan: Sterling Publishing Ltd.
Wilkie, W. (1965). Jordan’s Tropical Hygiene and Sanitation. United
Kingdom: Bullsie Tundal and Co.
www.uneb.or.jp/ietc/publications/freshwater/sb_summary.
index.aspx
Accessed 14/09/2012
228
UNIT 5 STATE AND FEDERAL REGULATORY
STANDARDS
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Water Resources in Nigeria
3.1.1 Features of Water Resources Management in
Nigeria
3.2 Water Laws in Nigeria
3.2.1 Customary Laws
3.2.2 Statutory Enactments
3.2.3 Federal Laws
3.2.4 State and Local Government Laws
3.3 The Fate of Existing Water Law.
3.4 The Way Forward for Water Laws in Nigeria
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/Further Reading
1.0 INTRODUCTION
From the previous units in modules two and three we saw how
beneficial water has been to human existence. Truly, water is one of the
natural resources man cannot toy with because if he does, negative
consequences will be reaped. In a bid to maximise all the potentials
inherent in water resources, it needs to be protected and covered by law
so that good control and management can be achieved.
Nigeria is a federation with federal, state and local government character
and all these shares in the responsibility of using and, protecting her
territorial waters. At present the surface water resources potential of the
country is estimated at 267.3 billion cubic metres while the groundwater
potential is 51.9 billion metres (NWRMP, 1995) and cited by Goldface-
Irokalibe (2008). These cannot be toyed with under an ideal situation.
But suffice it to say that water control and management is fragmented
and uncoordinated with the result that regulatory and monitoring
machine within the water sector in Nigeria is diverse, diffused and weak
in enforcing regulations.
EHS 304 MODULE 3
229
Present water laws lack proper provisions and mechanism for inter-
sectoral coordination, tariff setting and conflict resolution (Goldface-
Irokalibe, 2008).
2.0 OBJECTIVES
At the end of this unit, you should be able to:
discuss water resources in Nigeria
list the features of water resources management in Nigeria
explain water laws in Nigeria at federal, state and local
government levels
appraise the fate of the existing water laws in Nigeria
discuss the ways forward for water laws in Nigeria.
3.0 MAIN CONTENT
3.1 Water Resources in Nigeria
Nigeria, measuring about 924,000km2 in land area, located in West
Africa and lying entirely within the tropics where its climate is semi arid
in the North and humid in the south has annual rainfall which varies
from 4,000mm in the South-East to 250mm in the entire North-East.
The surface water resources potential of the country is estimated at
267.3 billion m3 while the ground water potential is 51.9 billion m
3
(NWRMP, 1995) and cited by Goldface-Irokalibe (2008).
Nigeria is divided into eight hydrological areas drained mainly by River
Niger and River Benue. These are in addition to their numerous minor
tributaries as well as Lake Chad and the Oguta Lake that discharge into
them.
We have other rivers like Gongola, Hadeija-Jama’are, Kaduna, Zamfara
and yobe in North and Ogun, Osun, Onni, Imo, Cross River and
Anambra in the south. Surface runoff and volume of available ground
water are all considerably large.
Generally, most of these rivers pass more than one state before entering
either Atlantic or Lake Chad.
According to Golddface -Irokalibe (2008), the total irrigation potential is
about 3.14 million ha comprising of:
230
2.04 million ha for formal former owned and managed schemes
based on conjunctive rise of surface water and shallow fadama
aquifers
1.1 million ha for formal public irrigation project which are under
government control.
The above water bodies are used for many purposes as indicated earlier,
yet we do not have strong laws or enforcement agents to protect them.
SELF-ASSESSMENT EXERCISE
Make a sketch of Nigerian map and show Rivers Niger and Benue with
their tributaries.
3.1.1 Features of Water Resources Management in Nigeria
(a) Weak data base: Water management cannot be done with poor
data management as no single pan Nigeria hydrological yearbook
has been published in the past ten years. Without water
assessment, there cannot be decision support system (DSS)
models necessary for understanding the impact of abstraction and
groundwater aquifers.
(b) Fragmented responsibility: Fragmented sectoral practice has
led to disjointed development and has critically led to a situation
where there is presently nothing in place to significantly ensure
the quality of water. There are no clear responsibilities, no
mandated water quality standards, no effective water monitoring,
no enforcement, no sanctions for polluters, no remediation and
thus no overall picture of the extent of the problem. These issues
are in the process of being tackled, though it must be observed in
a fragmented fashion as so many federal ministries are involved
in different aspects. These ministries are: Federal Ministry of
Agriculture and Water Resources, Federal Ministry of
Environment and Housing, Federal Ministry of Health and
various state agencies whose roles in quality of surface and
groundwater in Nigeria remain unclear.
(c) Weak institutional framework: The above comprised of River
Basin Development Authorities (RBDAs) and National Water
Resources Institutes (NWRI). The River Basin Development
Authorities (RBDAs) came into existence following the
promulgation of Decree 25 of 1976. The current law of RBDAs
(RBDA Act, cap 396) spells out diverse functions and objectives
for these authorities from which it may be inferred that their
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231
existence nationwide propels their acceptance as an appropriate
unit for water management.
Section 4 (1) (a) –(d) of the RBAA Act vest the authorities with
the legal powers to undertake comprehensive development of
both surface and underground water, to construct and maintain
dams, irrigation and drainage system, to supply water to all users
and to construct and maintain infrastructural services including
roads and bridges across project sites.
But the above law is found wanting as it made RBDA a supplier
and a consumer at the same time - a development manager and a
regulator of water resources. This engendered conflicts of
interest. Secondly, the operational domains of all River Basin
Development Authorities (RBDAs) are delineated by political
boundaries and not hydrological boundaries. With this
background, the staffing of these authorities seems to reflect
political composition of the states constituting the sphere of each
river basin authority. Therefore, there is no real coordination.
More so, the law governing RBDAs does not equip the
Authorities with power of enforcement neither does it stipulate
any penalty for defaulters. Finally, RBDAs do not have financial
independence and are severely cash strapped. To this effect, legal
proposals even where they have received ministerial approval are
not funded.
National Water Resources Institute (NWRI) has its enabling law
as NWRI Act; Cap 284 LFN 1990 with section 2 spelling out its
function. This empowers it to perform engineering research
function related to such major water resources project as may be
required for flood control, river regulation, reclamation, drainage,
irrigation domestic and industrial water supply, sewage and
sewage treatment.
The institution is further charged with the performance of other
functions related to planning of water resources management and
river basin development. Quite significantly, the institute has
specific legal mandate to promote the establishment of a uniform
national data collection system relating to surface and sub-surface
water resources. It is yet to fulfill this mandate owing to a variety
of factors including paucity of funds, shortage of skilled
manpower and inadequate equipment among others.
(d) Response to natural phenomena: Under this, we are made to
understand that controlling some natural phenomena like flood
232
and drought are being neglected by Nigerians and the
government. These are problems to water resource management.
More so, there has been shortage of manpower, insufficient
definition of land tenure and water rights and clear appreciation
of the interface between land and water rights. Also, there are
substantial investments gaps with insufficient attention paid to
the mobilisation of resources of private sector and civil society.
3.2 Water Laws in Nigeria
There is no denying the fact that there are water laws existing in Nigeria
and which govern the RBDAs, NWRI and so on. Below are such laws.
3.2.1 Customary Law
In all native community in Nigeria, there are customary laws relating to
water rights, thus, rules and regulations are known to and observed by
all and sundry. These laws are handed down orally from generation to
generation and are meant to preserve and protect the water quality.
Under customary laws, the common notion is that water course or water
bodies in any community is a resource common to all, subject to
community control and not capable of being owned privately. The only
apparent distinction was made in respect of private under- ground well
water which is not community owned. In some communities water
courses are associated with particular deities as owners. Though, such
publicly owned water (lake, streams or ponds) lie in privately owned
land, the communities guards them jealousy with community rules
regarding them being enforced by elders or traditional rulers.
3.2.2 Statutory Enactment
There are some laws that are old as Nigeria nation. Some are still in use.
Below is the list as prepared by Goldface-Irokalibe (2008).
Table 5.1: A list of Statutes on Water Resources in Nigeria
S/N
Name of statute Key provisions
1 The Water Works Act of
1915
Colonial Nigeria (shortly after
Amalgamation in 1914) passed the
law specifically to keep water from
being polluted. It prohibits the
pollution of water in Nigeria by
noxious or harmful matters.
2. The Minerals Act of 1917
(as amended ) now Cap
This law vests the Head of State of
Nigeria with power to make
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233
226 regulations for the prevention of
pollution of any water course.
3 The Public Health Act of
1917
It prohibits the fouling of water and
vitiation of the atmosphere.
4 The Oil in Navigable
Waters Act 1968
It prohibits water pollution by oil
spillage.
5 The petroleum Act, 1969 It covers prevention of pollution by
inland waters, rivers, lakes and water
course.
6 The River Basin
Development Authorities
(RBDA) Decree 25 of
1976 (repealed by No 87
of 1979 and also letter by
the RBDA Act, Decree 35
of 1987 is cap 396)
In its present form Cap. 396 spells
out diverse functions and objectives
for these authorities to ensure a pan-
Nigeria programme for water
resource development.
7 The Environmental Impact
Assessment (EIA) Decree
No. 86 of 1992
This law seeks to protect the physical
and aquatic environment.
8 Water Resource Decree
No. 101 of 1993
It vests the right to use and control
all surface waters and ground water
and of all water in any water course
affecting more than one state in the
federal government with provision
that any person may take water
without charge for his domestic
livestock watering purposes (in any
water course to which the public has
free access).
9 The 1999 Constitution of
the Federal Republic of
Nigeria
The constitution puts in the exclusive
legislative list (ELL) shipping and
navigation on the River Niger and its
affluents and on any such other
inland water way as may be
designated by the national assembly
to be an international water way or to
be an inter-state water way. The ELL
also includes water from such source
as may be declared by the National
Assembly to sources affecting more
than one state.
Yet there are still other regulations that bother on water resource in
Nigeria as can be seen below.
234
Table 5.2: A lists of other Regulations Bearing on Water Resource
in Nigeria
S/N Name of regulation Key provisions
1 National Policy on
Environment 1989
Protection of the environment
2 National Guidelines and
Standards for
Environmental Production
Control in Nigeria, 1991
Pollution control in water course as
part of the environment
3 National Efficient
Limitation Regulation 1991
Control of discharge of industrial
waste and sewage into water course
4 Pollution Abatement in
Industries and Facilities
Generating Wastes
Regulation 1991
Control of industrial pollution
5 Waste Management
Regulation 1991
Waste management
A closer look at table 1 above will reveal that some of these laws were
made by colonial authorities before the attainment of independence.
After independence, management became a trouble just as conformity to
the water laws; and the result has been obvious.
3.2.3 Federal Laws
From the federal stand point, there are three pieces of post colonial
legislation that form the core of water laws and the basis of water law
administration throughout Nigeria. The relevant laws are: River Basin
Development Authority Act, 1976, Water Resource Act, 1993 and the
Environment Impact Assessment Act, 1992. These laws form the
normative core whilst relevant rules and provision can be found in a
variety of sources including constitutional law, land law and mining law.
The Water Resources Act, 1993 vests ownership of water courses
affecting more than one state of the federation as well as all
underground water throughout the federation in the Federal Government
of Nigeria. By virtue of this law, the waters of all Nigeria’s trans-
boundary rivers and lakes belong to the federal government. By virtue of
section 2 of this law, anybody may take water without charge for his
domestic use, fishing or navigation and even from underground water
without any charge.
The Federal Ministry of Agriculture and Water Resources is the
relevant organ of the federal government charged with the responsibility
for management of the nation’s water resources. It does this by
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promoting the optimum planning, development and use of Nigeria’s
water resources and ensuring the coordination of all activities likely to
influence the quality, quantity distribution and management of water
resources. Additionally, the ministry has responsibility for ensuring the
application of appropriate standards and techniques for investigation,
use, control, protection, management and administration of water
resources.
3.2.4 State and Local Government Laws
At the state level, water edicts and by-laws form the legal basis and
authority for water use and management as far as they relate to intrastate
watercourse and water bodies. The present set up in Nigeria is such that
virtually every state of the federation has a state water agency (SWA)
with its enabling laws. These agencies deal with individual aspects of
water use to serve individual sectors of economy. The result of the
above is that there is the absence of an effective and functional water
resource management strategy which has left the various states and the
federal government pursuing their respective water agenda. Even at the
state level, water law exhibit similar characteristics as those of the
federal level.
At the local government level, it may be observed that customary law on
water use can be as important and binding as any written enactment in
regulating water resources related activities especially at the level of
rural community. A universally accepted principle is that all persons
within to the community have a right to use water passing through the
community. The water right so possessed by all is however, subject to
reasonable use. Reasonable right entails ensuring that the quality of
water is preserved.
3.3 The Fate of Existing Water Law
We have gone through the laws at all the tiers of the government –
federal, state and local government. The challenge now is to give a
summary of how the laws are fairing in Nigeria at present. The situation
on ground as given by Goldface-Irokalibe (2008) is hereby adopted.
Water supply and regulatory functions are often combined in a
single institution. This is true especially of all RBDAs as well as
all state water agencies.
Under present laws, different agencies at all tiers of government
pursue different water agenda. This approach has led to
fragmentation of water resource development policy issues,
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including abstraction, pollution control and watershed
management.
The regulatory and monitoring machinery within the water
sector in Nigeria is diverse, diffused and weak. Enforceability in
such circumstance becomes lax.
Virtually all laws on water resources (both federal and state) are
rule-oriented and fail to recognize the place and role of the
private sector and communities as important stakeholders.
Present laws lack proper provisions and mechanisms of inter-
sectoral co-ordination, tariff setting and conflict resolution.
At a point, state laws will have to synchronise with federal law
on water because water courses do not recognise state
boundaries. Thus, any system of regulation developed by a state
cannot stand in isolation.
SELF-ASSESSMENT EXERCISE
In your own thinking, what should be done to our water laws to improve
their effectiveness?
3.4 The Way forward for Water Laws in Nigeria
We are blessed to have already had some existing laws guiding the use
of our water resources. We will improve more if the following are
undertaken:
(A) Developing a new approach to enacting water laws: Attaining
sustainable development in Nigeria’s water sector is tied
inextricably to the enactment, establishment and enforcement of
standards, regulations, and legislation and control criteria on
water abstraction, pollution control, watershed management and
environmental management. Water laws and regulations should
become an effective tool for the management of water supply and
sanitation. The obligation of halting water quality degradation
and reversing pollution trends hinges on the promulgation of
action–centred methodologies backed by appropriate legislation
that are rightly enforced. Accordingly therefore, it is considered
issue that water laws, environmental legislation and related
regulations should be management–oriented, and not rule–
oriented. Whereas rule-oriented legislation emphases prohibition
and penalties as consequence for infringement and sanction
against violations of the law; management–oriented water supply
and environmental legislation must be founded on practical
incentives for the rational use and protection of water resources
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and for the promotion of sound water and environmentally
friendly policy that will foster sustainable development.
(B) Setting up a national water commission: In order to strengthen
policy on water resource standardisation, there is the
recommendation to set up a national water commission to fill up
the gap in good policy framework that has been lacking in the
previous arrangement. Its mandate should include the
development of the desired policy framework for water resource
management and to take charge of regulatory matters. As a
regulatory body, it should be granted an independent status that
will allow the regulatory and monitoring mechanism to operate
without pressure or influence from government or lobbyist so as
to pave way for a better enforcement process. As a regulatory
body, the commission will undertake the following:
granting water licenses against technical criteria
regulation and adjustment of prices (tariff setting)
monitoring service and quality standards (enforcement of
standards)
monitoring competition (checking monopoly abuses )
facilitating settlement of disputes (conflict resolution )
impose penalty for non-compliance
provide advice on other matters.
For the commission to function effectively towards the realisation of its
goals, its organisation should be so structured at federal state and local
level to allow for the participation of all stakeholders.
(C) Fair regulatory framework: The linkage between
political/bureaucratic power, and economic power should be
broken. It is possible to achieve this through the separation of
responsibility for the building of water infrastructure. The
separation will also enhance the termination of inter –
institutional conflict and politics which has resulted in certain
government agencies and upper strata citizens paying little or
nothing for water consumption. More so, a regulatory framework
based on participatory management will be fair to all. Thus,
participatory water resources management will have the people as
its focus and major priority Finally, the process of enforcement
must be fair and just; and must not be seen to tilt in favour of the
high and mighty in the society.
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4.0 CONCLUSION
From all the discussions so far, one can conclude this by saying that
right from the time of the beginning of Nigeria as entity nation, efforts
were made to protect her water resources through setting regulatory
standards. Such efforts were plagued with many loopholes. Further laws
made after the exit of the colonial masters for the same purposes did not
improve the situation much as conflicts still exist due to the unclear
boundaries between federal, state and local government laws protecting
our territorial waters. However, if modifications are made and followed
to the letter, there could be a brighter future for Nigeria water resources.
5.0 SUMMARY
From all that have been learnt so far, we can summarise as follows:
Nigeria as a country has great potentials in terms of water
resources acquisition and has eight hydrological areas at her
disposal.
Water resource management in Nigeria has not been having it all
good as it has visible signs to support the above chain. Thus weak
data base, fragmented responsibilities and weak institutional
framework have been the characteristics of water management
and regulation in Nigeria with the result that there is no co-
ordination of ideas, instead divergent views or opinions are held
and enforceability is zero.
There have been water laws in Nigeria with the first ones made
by our colonial masters and others later made by Nigerians.
These laws come under the statutory enactments. There are also
the customary laws which are meant to protect water in various
communities. There are also federal laws. One noticeable fact
about the federal and state laws is that there are clashes of interest
and weaknesses in terms of implementing these laws.
The fate of existing water laws in Nigeria is that there have been
unclear definition of roles and enforceability of the existing laws.
If Nigerians want, they can make things better for themselves in
terms of solving all the anomalies found in the management of
water resources, make new ones that will be suitable and ensure
unbiased compliance by setting up a functional national water
commission.
6.0 TUTOR-MARKED ASSIGNMENT
1. (a) Enumerate the features of water resource management in
Nigeria.
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(b) List at least six statutes on water resource management.
2. What is the way forward for Nigeria water laws?
7.0 REFERENCES/FURTHER READING
Constitution of Federal Republic of Nigeria, 1999. Draft National Water
Resources Management Policy 2007.
Environmental Impact Assessment Act, LFN, 2004. Goldface-Irokalibe
I. .J. (2008). Water Management in Federal and Federal–
Type Countries: Nigeria perspectives. Zaria: Ahmadu Bello
Univeristy Zaira, Nigeria.
Goldface –Irokalibe, I. J. (1999). The Application of Water Resources
Decree to the Development and Management of River Basin
Development Authorities. CJLJ. Vol. 5 No. 5.
Goldface – Irokalibe, I. .J. (2002). Towards an effective Legal and
Institutional framework for Integrated Water Resources
Management in Nigeria. A.B.U. Zaria.
Goldface – Irokalibe et al. (2001) WRMS, Legal and Regulatory
Framework (GAC) Final Report FMWR.
Musa, I. K. (2008). NIWRMA memo FMAWR Abuja, Nigeria. Water
Resource Act LFN, 2004.
Wouters, P. ( 2000). National and International Water Law: Achieving
Equitable and Sustainable Use of Water Resources. Carbondale:
Water International.