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UNIVERSITY OF NAIROBI
Pollution Profile for Enkare Narok River
By Christopher Kiratu, F16/1327/2010
A project submitted as a partial fulfillment for the requirement for the
award of the degree of
BACHELOR OF SCIENCE IN CIVIL ENGINEERING
2015
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Abstract
Rivers which run across urban centers around the world are exposed to a constant threat of
pollution and degradation by human activities. This is due to the fact that urban centers are
densely populated and harbor a myriad of economic activities such as industries. The effluents
produced thereof coupled with the waste water (about 80% of water used by the population) end
up in the river in one way or another. This demands constant water quality monitoring and
measures to preserve the health of the rivers.
A classic example of a river which has suffered pollution as it runs through an urban center is the
Nairobi River.
This project sought to determine the pollution profile of the Enkare Narok River which runs
through Narok town, and to establish the contribution of the town activities to this pollution.
Four sampling stations were chosen along the river. The first one (S1) measured the quality of
the river before it interacted with the town while the last one (S4) checked the quality as the river
water flowed past the town boundaries. The other two stations lay between the first and the last.
For each station the following water quality monitoring parameters were tested: pH, electrical
conductivity, temperature, dissolved oxygen, BOD, COD, nitrates, iron, total coliform counts,
total suspended solids, total dissolved solids and the total solids. Sampling was done during the
wet and dry period. A comparison of these parameters was made across the four stations and
against the Environmental Management & Coordination Water Quality Regulations, 2006
standards.
It was found out that the river was slightly polluted and point source pollution identified as the
highest contributor to this. Relevant recommendations were put forward to address this issue.
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Dedication
To my mother Esther and my brother Michael
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Acknowledgements
I would like to thank the following persons whose contributions have made this project a
success.
1. My supervisor, Eng. J. N. Gitonga for his guidance throughout the project time.
2. The Narok WRMA sub-region office, District Agricultural office, KNBS Narok district
office and the Narok Water Supply and Sewerage Company for graciously assisting me
with all the information I required from you.
3. Wambui, Joy and Kaunda from the University of Nairobi Public Health Engineering
laboratory for your assistance during testing of water samples.
4. The Civil Engineering class of 2015 for your support and positive criticism
5. My family for your love, support and encouragement
Above all I thank the Almighty God who has brought me this far.
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Table of Contents
Abstract………………………………………………………………………………………………ii
Dedication…………………………………………………………………………………………...iii
Acknowledgements………………………………………………………………………………….iv
Table of Contents……………………………………………………………………………....…….v
List of tables………………………………………………………………………………………..vii
List of Figures………………….…………………………………………………………………..vii
List of Plates………………………………………………………………………………………..vii
List of Abbreviations………………………………………………………………………….…...viii
1 INTRODUCTION ................................................................................................................................ 1
1.1 Background Information ............................................................................................................... 1
1.2 Problem Statement ........................................................................................................................ 2
1.3 Study Objectives ........................................................................................................................... 2
2 LITERATURE REVIEW ..................................................................................................................... 3
2.1 Introduction ................................................................................................................................... 3
2.2 River Pollution .............................................................................................................................. 5
2.2.1 Uses of River Water .............................................................................................................. 5
2.2.2 Causes and Nature of River Pollution ................................................................................... 6
2.2.3 Detection and Measurement of River Pollution .................................................................... 7
2.2.4 Self-Purification of Rivers .................................................................................................... 8
2.2.5 Water Quality Standards for Rivers .................................................................................... 10
2.2.6 Legal Framework on Water Resources and Pollution ......................................................... 11
3 RESEARCH METHODOLOGY ........................................................................................................ 19
3.1 The study area ................................................................................................................................... 19
3.2 Sampling ..................................................................................................................................... 20
3.3 Limitations of the study .............................................................................................................. 21
3.4 Laboratory Examination of Samples ........................................................................................... 21
3.4.1 pH ........................................................................................................................................ 21
3.4.2 Temperature: ....................................................................................................................... 22
3.4.3 Electrical Conductivity (Specific Conductivity): ................................................................ 23
3.4.4 Biochemical Oxygen Demand (BOD) ................................................................................ 24
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3.4.5 Chemical Oxygen Demand (COD) ..................................................................................... 25
3.4.6 Dissolved Oxygen (DO) ...................................................................................................... 26
3.4.7 Total Coliform counts ......................................................................................................... 27
3.4.8 Nitrates ................................................................................................................................ 28
3.4.9 Iron ...................................................................................................................................... 28
3.4.10 Turbidity ............................................................................................................................. 29
3.4.11 Solids ................................................................................................................................... 29
4 RESULTS AND ANALYSIS ............................................................................................................. 31
4.1 pH: .............................................................................................................................................. 32
4.1.1 Temperature ........................................................................................................................ 32
4.1.2 Electrical conductivity ........................................................................................................ 33
4.1.3 BOD .................................................................................................................................... 34
4.1.4 COD .................................................................................................................................... 35
4.1.5 DO ....................................................................................................................................... 36
4.1.6 Total Coliform counts ......................................................................................................... 38
4.1.7 Nitrates ................................................................................................................................ 39
4.1.8 Iron ...................................................................................................................................... 40
4.1.9 Turbidity ............................................................................................................................. 41
4.1.10 Total Solids ......................................................................................................................... 42
4.2 The Pollution Profile ................................................................................................................... 44
5 CONCLUSIONS AND RECOMMENDATIONS ............................................................................. 51
5.1 Conclusion: ................................................................................................................................. 51
5.2 Recommendations: ...................................................................................................................... 52
6 REFERENCES ................................................................................................................................... 53
7 APPENDICES: ................................................................................................................................... 54
7.1 Appendix 1 .................................................................................................................................. 54
7.2 Appendix 2 Plates ....................................................................................................................... 61
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List of Figures
Fig. 1 Deoxygenation, oxygenation and the oxygen sag ............................................................... 9
Fig. 2 Water resources management institutional framework ..................................................... 12
Fig. 3 The sampling points........................................................................................................... 20
List of Tables
Table 1: Quality Standards for Sources of Domestic Water ......................................................... 54
Table 2: Standards for Effluent Discharge into the Environment ................................................. 55
Table 3: Microbiological Quality Guidelines for Wastewater Use in Irrigation .......................... 58
Table 4: Standards for Irrigation Water ........................................................................................ 58
Table 5: Quality Standards for Recreational Waters .................................................................... 59
List of plates
Plate 1 – 3: an abandoned quarry where raw sewage from septic tanks in the town is
dumped …………………………………………………………………………………………. 61
Plate 4: an exhauster services vehicle heading to the abandoned quarry to empty its
contents………………………………………………………………………………………......61
Plate 5 Car wash activities along the river ……………………………………………………....61
Plate 6 Maasai cattle coming from the river for a drink ………………………………………….….61
Plate 7: A dried up lagoon where sewage used to be dumped …………………………….....….62
Plate 8 – 10: a view of the drain that empties the town’s effluents and storm water to the river.
This was identified as the main point source pollution…………………………………….…….62
Plate 11: Sampling; temperature measurement at sampling station S1 …...……………….……63
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List of Abbreviations
BOD – Biochemical Oxygen Demand
CAAC – Catchment Areas Advisory Committees
COD – Chemical Oxygen Demand
DO – Dissolved Oxygen
EMCA- Environmental Management and Coordination Act
EMCWQR – Environmental Management and Coordination Water Quality Regulations, 2006
FTU – Formazin Turbidity Units
KEWI – Kenya Water Institute
KNBS – Kenya National Bureau of Statistics
MPN – Most Probable Number
NEMA – National Environment Management Authority
NIB – National Irrigation Board
NWCPC – National Water Conservation and Pipeline Company
UNESCO – United Nations Educational and Scientific Organization
UNEP – United Nations Environmental Programme
WAB – Water Appeals Board
WHO – World Health Organization
WRMA – Water Resources Management Authority
WSB – Water Service Board
WSRB – Water Services Regulatory Board
WSP – Water Service Providers
WSTF – Water Service Trust Fund
WRUA – Water Resource Users Association
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Chapter One
1 INTRODUCTION
1.1 Background Information
Narok town is the district capital of Narok County with an area of approximately 215.4 km2.
According to the 2009 national census, the population of the town is about 67,505 which
represent a 64% increase from that recorded in the 1999 census. The town is an administrative
center of the county in that it houses the major county government and national government
offices. Similarly, it is the business hub of the county as it harbors the major commercial banks
operating in the county, whole sale and retail outlets and hotels given that Narok County is a
tourist destination.
Around the town are six major boarding high schools, eleven primary schools, a polytechnic and
a university. In a nutshell, Narok is a fast growing town. The natives of Narok town are the
pastoralist Maasai community, who mostly live outside the town. The various economic
activities present have attracted many inhabitants making Narok a cosmopolitan town.
There are no industries existing in the town. The main economic activities around the town are
wheat and maize farming, businesses and hotels as well as nomadic pastoralism for the native
Maasai community. Thus the water demand of the town is for domestic use in homes and schools
and for watering the animals. Irrigation is done on a very small scale along the Enkare Narok
River to grow vegetables.
The water used by the residents comes mainly from the Enkare Narok River which conveniently
runs through the town.
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1.2 Problem Statement
The Enkare Narok River is a permanent river which draws its water from the Mau forest. It runs
through Narok town and eventually drains into the Lake Natron. Among the six catchment areas
designated by the Water Resources Management Authority (WRMA) for water resources
management, the Enkare Narok River falls under the Rift Valley Catchment Area.
The land on which Narok town stands is a water shed. Two of the tributaries that feed the river
intersect within the town boundaries. This is where the animals belonging to the pastoralist
Maasai community used to rest after being watered in the afternoon. The town sits bottom of the
sloping land and it is indeed an encroachment to the river. It is marred by frequent flooding from
storm water when it rains heavily as the land is being drained of surface runoff.
The town does not have a sewerage system or an elaborate waste collection and disposal system.
Septic tanks are used which are emptied by exhauster services and dumped in abandoned
quarries outside town. (See appendix 2)
The existence of this town along the river poses a pollution problem both directly and indirectly
such as when the storm water sweeps all forms of loads from the town into the river. Keeping in
mind that this river is responsible for watering this community and their animals, it is imperative
that action needs to be taken to safeguard the water quality of the river.
This study seeks to establish the pollution profile of the river and the contribution of the Narok
town residents to its pollution and to recommend appropriate measures to mitigate the same.
1.3 Study Objectives
1. To determine the pollution profile of the Enkare Narok river and the contribution of the
Narok town residents to this pollution
2. To recommend measures that can be taken to mitigate the above
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Chapter Two
2 LITERATURE REVIEW
2.1 Introduction
Water is life. The fundamental importance of water for life on earth needs little justification if
any. Indeed man’s life revolves around water. For example about 70 per cent of our bodies are
made of water. Not a day ends without man interacting with water; be it the shower in the
morning, a cup of coffee or even the glass of water beside you as you are reading this. It is clear
that the interaction between man and water is inevitable. A part from the physiological processes
in our bodies and for domestic use, man requires water for farming and irrigation, industry,
navigation, recreation, power generation among others.
Sadly, it is this interaction with water and the environment at large coupled with the fact that
man will sacrifice anything in order to make his life more pleasant and convenient that has given
birth to pollution.
The World Water Development Report 3 ‘Water in a changing world’ refers to pollution as
chemicals or substances in concentrations larger than would occur under natural conditions.
(UNESCO 2009)
The Environmental Management and Coordination Act, 1999 defines pollution as ‘any direct or
indirect alteration of the physical, thermal, chemical, biological, or radio-active properties of any
part of the environment by discharging, emitting, or depositing wastes so as to affect any
beneficial use adversely, to cause a condition which is hazardous or potentially hazardous to
public health, safety or welfare, or to animals, birds, wildlife, fish or aquatic life, or to plants or
to cause contravention of any condition, limitation, or restriction which is subject to a license
under this Act’
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Water pollution can therefore be defined as that which is due to adding something which changes
the natural quality water so the riparian owner does not receive the natural quality of the stream.
The United Nations International Decade for action campaign dubbed “Water for Life” 2005-
2015 report makes the following observations on water pollution:
Every day, 2 million tons of sewage and other effluents drain into the world's waters.
Every year, more people die from unsafe water than from all forms of violence, including
war
The most significant sources of water pollution are lack of inadequate treatment of
human wastes and inadequately managed and treated industrial and agricultural wastes.
80% of sewage in developing countries is discharged untreated directly into water bodies.
It is clear that man in his endeavors is solely responsible for pollution of the water resources in
the world. For instance, man alters the size, shape, texture and position of the stream channel. He
alters the drainage to the stream, ground water level and the stream quality, speed and turbulence
of the flow within the stream. Such changes are made for flood protection and prevention,
drainage and irrigation of farmland, use of water supply for settlement and industry, including
mines, waste disposal commercial and recreational proposes. He also alters the land use and this
changes the chemical and physical characteristics of the streams draining that land.
The changes caused to the original vegetation such forest encroachment for settlement decrease
precipitation and increase the speed of runoff and erosion thus altering the flow and increasing
sedimentation in the streams.
The sources of water pollution can be broadly classified as those coming from:
i. Domestic effluents which include sewage both treated and untreated,
ii. Industrial effluents which include organic effluents from sugar, dairy, oil and other
petrochemical works as well as inorganic effluents from steel works, car and other heavy
industries; particles dust and metals from mines and quarries and wash from gravel
extractions
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iii. Farming and agricultural activities: they alter the physical and chemical states of rivers
due to use of fertilizers, pesticides and herbicides. Ploughing and tillage, burning of
vegetation and deforestation increase sediment yield in streams.
iv. Storm water: it carries various types of wastes from dead leaves and animals to heavy
metals petrochemicals, bitumen and tire derivatives depending on the land use and the
places it flows through.
2.2 River Pollution
2.2.1 Uses of River Water
The water in the rivers has its origin from precipitation especially rain. The other forms of
precipitation involved include hail, snow and sleet. Part of this precipitation infiltrates into the
soil and used by plants for growth and their physiological processes while the rest percolates the
ground and is stored as ground water. This is used to form underground streams and springs
which in turn recharge our rivers.
A fraction of this rainfall finds its way into the river systems either as surface runoff or as
channel precipitation. The river flow thus increases. The process of evaporation leads to
formation of vapor which in turn condenses leading to precipitation. And the cycle continues ad
inifinitum.
The water which percolates through the soil makes accounts for the presence of dissolved salts,
organic and suspended matter, and dissolved gases such as oxygen, nitrogen and carbon dioxide
in the river water. The activities of man however may lead to alterations in the natural
composition of river water. There various uses of river water as discussed below.
Rivers have been used from time immemorial for providing drinking water for both man and the
animals. Drinking water should be pure and wholesome; free from visible suspended matter,
color, odor, and taste; from all objectionable bacteria indicative of the presence of disease
producing organisms, and contains no dissolved matter of mineral or organic origin which in
quantity or quality would render it dangerous to health, and will not dissolve substances injurious
to health (Taylor, 1958).
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In a nut shell, drinking water should be reasonably soft and should not have a ‘flat taste.’
Generally most river water in the world is unfit for drinking directly, and some treatment is
required depending on the level of impurities. Some of the method used for treatment of water
for drinking purposes include: screening and straining, aeration, softening, sand filtration,
coagulation with chemicals and chemical treatment to reduce corrosiveness.
Generally, agricultural activities are concentrated along rivers. This is due to the fact that flood
plains are usually very fertile as a result of the various nutrients deposited when the river
overflows. Similarly, rivers are a source of water for irrigation. The fact that a river flows makes
it a favorite for this task since at any one time a new and fresh amount of water is passing at a
given point along the river. There are various methods of drawing water from the river for
irrigation. These include: direct river diversion where an off- take canal is dug through the river
bank; river diversion by use of a weir which overcomes the problems of fluctuating water levels
in the river; and pumping which is a little bit more expensive than the aforementioned methods.
Other uses include fisheries, industry, and disposal of waste waters, navigation, recreation, and
recharge of ground water.
2.2.2 Causes and Nature of River Pollution
The National water quality management strategy 2012 – 2016 notes that most Kenyan rivers are
adversely affected by human activities. These activities discharge various loads to the rivers. The
rivers have a capacity of diluting the loads in a process called self-purification but they can only
dilute so much. Thus if the load is too high, the river’s capacity to self-purify itself is lost and it
becomes a ‘dead’ river. A good example is the upper Athi.
The main pollutants affecting Kenyan rivers are identified as follows:
All types of sediments
Untreated municipal wastes
Fecal matter from pit latrines
Untreated industrial effluent
Untreated storm water
Leachates from solid waste dumps
Agrochemical and pesticide residues
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Nutrients, such as nitrogen and phosphorus
Mining wastes
2.2.3 Detection and Measurement of River Pollution
River pollution is detectable in many ways. For example, by simple observation, if river water
has changed in color, or has suspended solids in it or is very turbid or even has an odor is an
indication of pollution. However this is not quantifiable and therefore more elaborate and
scientific methods are required in order to give details of the quantity and nature of the
substances polluting the water and shed light on the possible measures to mitigate the same.
There exist water quality standards in the country and the parameters that are used to determine
the same in the Environmental Management and Co-Ordination (Water Quality) Regulations,
2006. (See section 2.2.4 below). Therefore to determine whether or not a river is polluted and the
extent of the pollution, the parameters outlined in the regulations are measured and the results
compared with the maximum allowable limits.
The Environmental Management and Co-Ordination (Water Quality) Regulations, 2006 gives a
general format of monitoring the quality of water for various purposes against pollution. This is
outlined in the schedules as follows:
Second Schedule : Quality Monitoring for Sources of Domestic Water
Fourth Schedule : Monitoring Guide for Discharge into the Environment
Sixth Schedule : Monitoring for Discharge of Treated Effluent into the Environment
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2.2.4 Self-Purification of Rivers
Provided that a river is not polluted to a critical condition, it is able to get rid of the polluting
agents thus maintaining its quality and ecosystem balance. It involves a complex system of
chemical, physical and biological processes.
Biological self-purification is the process in which organic wastes are broken down by the
respiration of micro-organisms into stable end products. It is a biochemical oxidation process
through which organic wastes are consumed leaving behind end products such as carbon dioxide,
water, phosphates and nitrates. The water is purified in the sense that the concentration of waste
material has been reduced. (Whitehead P.G, Lack T, 1982)
While the process of self-purification takes place through biochemical respiration, oxygen gets
used up. If the oxygen supply to the river is exceeded by the demand in the process an anaerobic
condition occurs inhibiting the process. Therefore dissolved oxygen is critical in the process of
self-purification.
Streeter and Phelps (1925) analyzed the variation of dissolved oxygen downstream of a point of
discharge into the river. The equations produced thereof represent the oxygen balance and a
schematic called the oxygen sag was developed showing the processes of biochemical oxidation
as the only sink and atmospheric reparation as the only source of oxygen. (Whitehead P.G , Lack
T, 1982)
The oxygen deficit at any point during the self-purification process is the difference between the
saturation DO content and the DO content at that point.
Oxygen deficit D, = saturation DO – Actual DO
The variation of oxygen deficit (D) with the distance along the stream, and hence with the time
of flow from the point of pollution is depicted by the ‘Oxygen Sag Curve’ (Fig. 2). The major
point in sag analysis is point of minimum DO, i.e., maximum deficit. The maximum or critical
deficit (Dc) occurs at the inflexion points of the oxygen sag curve (M. M Ghangrekar, 2005)
Do – initial DO
Dt – DO at time t
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Dc – Critical DO
tc – time for critical DO
Fig. 1 Deoxygenation, oxygenation and the oxygen sag
When wastewater is discharged in to the stream, the DO level in the stream depletes with time.
(deoxygenation.) The rate of deoxygenation depends on the amount of organic matter remaining
(Lt), to be oxidized at any time t and temperature (T) at which reaction occurs. The variation of
depletion of DO content of the stream with time is depicted by the deoxygenation curve in the
absence of aeration. The ordinates below the deoxygenation curve (Fig. 2) indicate the oxygen
remaining in the natural stream after satisfying the bio-chemical demand of oxygen.
As the DO content of the stream is gradually consumed the atmosphere supplies oxygen
continuously to the water, through the process of re-aeration (reoxygenation). The two processes
are continuous. The rate of reoxygenation depends on:
i. Depth of water in the stream: the shallower the stream the higher the rate of reaeration
ii. Velocity of flow in the stream: rate of aeration increases with velocity of flow
iii. Oxygen deficit below saturation DO: since solubility rate depends on difference between
saturation concentration and existing concentration of DO.
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iv. Temperature of water: solubility of oxygen in the river is lower at higher temperature and
also saturation concentration is less at higher temperature.
2.2.5 Water Quality Standards for Rivers
As aforementioned, river water has many uses which can be broadly classified (for the purpose
of this study) into domestic use, industrial use, agricultural use and for recreational purposes.
Therefore the quality standards will be explored under these four thematic areas. These water
quality standards will be governed by the Environmental Management and Coordination, (Water
Quality) Regulations 2006 (EMCWQR, 2006), created by the Minister for Environment and
Natural Resources in consultation with lead agencies in exercise of the powers conferred to him
by the Environmental Management and Coordination Act, 1999 Section 147. The regulations are
applicable to water meant for the following uses: Drinking, Industry, Agriculture, recreation,
wildlife and fisheries as well as other uses.
2.2.5.1 Water Quality for Domestic Use
Domestic water use mainly entails drinking, cooking, bathing, washing, flushing toilets as well
as the watering of lawns and gardens. The quality standards set for the sources of water for use in
domestic purposes are spelt out in the First Schedule of the EMCWQR, 2006. (See appendix 1,
table 1)
2.2.5.2 Water Quality for Industrial Use and Effluent Discharge
The quality standards available from the EMCWQR, 2006 are standards for effluent discharge
into aquatic environment, to avoid pollution of the same. That notwithstanding, the regulations
mention that the water used for trade or industrial undertakings should comply with the standards
set by the competent lead agency in regard to that particular activity. The standards for discharge
into aquatic environment as enumerated in the Third Schedule of the EMCWQR, 2006. (See
appendix 1 table 2)
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It is important to note that anyone who needs to discharge effluent into the aquatic environment
is required to apply for an effluent discharge license and to pay some prescribed fee.
(EMCWQR, 2006 Part III section 16 & 17)
2.2.5.3 Water Quality for Agricultural Use
In agriculture, water is mainly used for irrigation purposes. EMCWQR, 2006 in part IV section
19 prohibits the use of waste water for irrigation purposes unless it meets the standards set out in
the Eighth Schedule. (See appendix 1 table 3)
Section 20 of the EMCWQR, 2006 states that water abstracted from a water body for irrigation
purposes must meet certain standards. These standards are found in the Ninth Schedule. (See
appendix 1 table 4)
2.2.5.4 Water Quality for Recreational Purposes
Recreation basically refers to any activity of leisure, done for pleasure enjoyment or amusement
or fun. There are various recreation activities involving water, namely those that involve contact
with water such as swimming, boating and canoeing, white water rafting and surfing. Others that
may not require contact with water but at the same time require water include fishing picnics by
the river as well as nature viewing. Part V section 25 of the EMCWQR, 2006 gives the quality
standards of any natural water body that is to be used for recreational purposes. These standards
are enumerated in the Tenth Schedule. (See appendix 1 table 5)
2.2.6 Legal Framework on Water Resources and Pollution
The Water Act 2002 is the basic legal framework for the management of the water resources in
Kenya. It was established as an Act of Parliament to provide for the following:
i. the management, conservation, use and control of water resources
ii. acquisition and regulation of rights to use water;
iii. to provide for the regulation and management of water supply and sewerage services;
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It was also meant to repeal the Water Act (Cap. 372) and certain provisions of the Local
Government Act; and for related purposes. The Act also was a tool and an instrument for the
implementation of the National Water Policy.
The National Water Policy was first adopted by Parliament as Sessional paper No. 1 of 1999 in
April 1999, and launched in August of the same year for implementation. Its main objective was
a management handover of the ownership of water facilities to communities for their operation
and maintenance. It stated that the government would hand over urban water systems to
autonomous departments within local authorities and the rural water supplies to communities
thereby excluding the government from direct service provision restricting it to regulatory
functions.
The Water Act 2002, Part II Section 3 states that, “Every water resource is hereby vested in the
State, subject to any rights of user granted by or under this Act or any other written law.” This
simply means that the State owns all ground and surface water resources and that the exploitation
of the same requires authority granted via the issuance of a water permit. The Act goes ahead to
establish the institutional framework responsible for overseeing the management of the water
resources in the country (Part III).
The institutional framework is summarized in the diagram below:
Fig. 2 Water resources management institutional framework
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The institutional framework is basically pyramidal in structure. The Ministry of Water and
Irrigation sits at the apex and is responsible for policy formulation, i.e. development of
legislation, sector coordination and guidance, monitoring and evaluation. The policies that the
Ministry is expected to formulate include:
a. Water Resources Management Policy
b. Water and Sanitation Services Policy
c. Water Quality and Pollution Control Policy
d. Flood Control and Land Reclamation Policy
e. Waste Water Treatment and Disposal Policy
f. National Irrigation Policy
g. Water Schemes and Community Water Projects
The institutions responsible for regulation of both water resources management and water and
sewerage service are the Water Resources Management Authority (WRMA) and the Water
Services Regulatory Board (WSRB) respectively which operate at the national level each having
distinct duties. WRMA manages, regulates, apportions, protects and conserves the water
resources in the country up to and including trans-boundary waters. WSRB on the other hand is
charged with monitoring and regulating the water services boards in the country as well as
setting standards for provision of water services and developing guidelines for water tariffs.
Service provision at the regional level is carried out by Water Service Boards (WSBs) for water
and sewerage services while the regional WRMA office and the Catchment Areas Advisory
Committees (CAACs) oversees water resources management.
At the local level, service provision for water and sewerage services is executed by Water
Service Providers (WSPs) while water resources management is overseen by Water Resource
Users Associations (WRUAs).
The Water Appeals Board (WAB), the National Water Conservation and Pipeline Corporation
(NWCPC), the National Irrigation Board (NIB), the Kenya Water Institute (KEWI), and the
Water Services Trust Fund (WSTF) operate at the national level.
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Thus the duty of formulating policies with regard to water quality and pollution control in the
country lies with the Ministry of Water And Irrigation.
From an environmental perspective, the Environmental Management and Coordination Act, 1999
was enacted to harmonize the management of the country’s environment. Part III section 4(1) of
the Act has established a council known as the National Environmental Council whose mandate
under section 5 is to:
a) Be responsible for policy formulation and directions for purposes of this Act
b) Set national goals and objectives and determine policies and priorities for the protection
of the environment
c) Promote co-operation among public departments, local authorities, private sector, Non-
Governmental Organizations and such other organizations engaged in environmental
protection programmes
d) Perform such other functions as are assigned under this Act.
Section 7 of the same Act establishes the National Environment Management Authority (NEMA)
whose object and purpose is spelt out in section 9 (1) as ‘to exercise general supervision and co-
ordination overall matters relating to the environment and to be the principal instrument of
Government in the implementation of all policies relating to the environment.’ This basically
makes NEMA the environmental watchdog. The functions of NEMA as stipulated in the Act
include the following:
i. Co-ordinate the various environmental management activities being undertaken by the
lead agencies and promote the integration of environmental considerations into
development policies, plans, programmes and projects with a view to ensuring the proper
management and rational utilization of environmental resources on a sustainable yield
basis for the improvement of the quality of human life in Kenya
ii. Take stock of the natural resources in Kenya and their utilization and conservation
iii. Establish and review in consultation with the relevant lead agencies, land use guidelines
iv. Examine land use patterns to determine their impact on the quality and quantity of natural
resources
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v. Advise the Government on legislative and other measures for the management of the
environment or the implementation of relevant international conventions, treaties and
agreements in the field of environment, as the case may be
vi. Identify projects and programmes or types of projects and programme, plans and policies
for which environmental audit or environmental monitoring must be conducted under this
Act
vii. Monitor and assess activities, including activities being carried out by relevant lead
agencies, in order to ensure that the environment is not degraded by such activities,
environmental management objectives are adhered to and adequate early warning on
impending environmental emergencies is given
viii. Undertake, in co-operation with relevant lead agencies, programmes intended to enhance
environmental education and public awareness about the need for sound environmental
management as well as for enlisting public support and encouraging the effort made by
other entities in that regard
ix. Publish and disseminate manuals, codes or guidelines relating to environmental
management and prevention or abatement of environmental degradation
x. Render advice and technical support, where possible, to entities engaged in natural
resources management and environmental protection so as to enable them to carry out
their responsibilities satisfactorily
Part V Section 42 of the Environmental Management and coordination Act, 1999 gives
guidelines on the protection of rivers lakes and wetlands. It prohibits the following activities near
or in a river wetland or lake without prior written approval from the Director-General after an
environmental impact assessment has been carried out on the same:
i. Construction or reconstruction of structures
ii. Excavation or drilling that may disturb the river or lake or wetland
iii. Introduction of an indigenous or foreign animal or plant specimen to the river, lake or wetland
iv. Deposition of substances in the river, lake or wetland that may adversely affect the environment
on them
v. Blocking or diversion of the river, lake or wetland from its normal course
vi. Drainage of any lake, river or wetland
16
The above guidelines are emphasized by the Environmental Management and Coordination
(Water Quality) Regulations, 2006 Legal notice no.120 which states in Part II Section 6 that “no
person shall:
a) Discharge, any effluent from sewage treatment works, industry or other point sources into
the aquatic environment without a valid effluent discharge license issued in accordance
with the
provisions of the Act.
b) abstract ground water or carry out any activity near any lakes, rivers, streams, springs and
wells that is likely to have any adverse impact on the quantity and quality of the water,
without an Environmental Impact Assessment license issued in accordance with the
provisions of the Act; or
c) Cultivate or undertake any development activity within a minimum of six meters and a
maximum of thirty meters from the highest ever recorded flood level, on either side of a
river or stream, and as may be determined by the Authority from time to time.”
Similarly, section 42 (2) of the Environmental Management and coordination Act, 1999 gives
the Minister (for environment) power to declare a lake shore, wetland, coastal zone or river bank
a protected area and impose restrictions to protect the same via a gazette notice. Section 42 (3)
gives the Minister (for environment) the power to issue general and specific orders, regulations
or standards via a gazette notice for the management of river banks, lake shores, wetlands or
coastal zones for conservation and protection against environmental degradation. Among the
provisions under this section are contingency plans for the prevention and control of all
deliberate and accidental discharge of pollutants into the sea, lakes or rivers. (Section 42 (3) (e))
Section 42 (4) empowers NEMA (in consultation with relevant lead agencies) to issue guidelines
for the management of the environment of rivers and lakes. Section 42 (5) concludes by stating
that ‘any person who contravenes or fails to comply with any orders, regulations or standards
issued under this section shall be guilty of an offence.’
Part VIII section 72 (of the Environmental Management and Coordination Act, 1999) prohibits
the pollution of water. Section 72 (1) states that:
17
“Any person who upon the coming into force of this Act, discharge or applies any poison, toxic,
noxious or obstructing matter, radioactive waste or other pollutants or permits any person to
dump or discharge such matter into the aquatic environment in contravention of water pollution
control standards established under this Part shall be guilty of an offence and liable to
imprisonment for a term not exceeding two years or to a fine not exceeding one million shillings
or to both such imprisonment and fine.”
Section 72 (2) continues as follows:
“A person found guilty under subsection (1) shall, in addition to any sentence or fine imposed on
him:-
a) Pay the cost of the removal of any poison, toxic, noxious or obstructing matter,
radioactive waste or other pollutants, including the costs of restoration of the damaged
environment, which may be incurred by a Government agency or organ in that respect;
b) Pay third parties reparation, cost of restoration, restitution or compensation as may be
determined by a court of law on application by such third parties.”
Part XIII section 142 elaborates on the offences relating to pollution. It goes thus:
“142. (1) any person who:-
a) discharges any dangerous materials, substances, oil, oil mixtures into land, water, air, or
aquatic environment contrary to the provisions of this Act;
b) pollutes the environment contrary to the provisions of this Act;
c) discharges any pollutant into the environment contrary to the provisions of this Act;
Commits an offence and shall on conviction, be liable to a fine not exceeding five hundred
thousand shillings.
(2) In addition to any sentence that the Court may impose upon a polluter under subsection (1) of
this Section, the Court may direct that person to: –
a) Pay the full cost of cleaning up the polluted environment and of removing the pollution;
b) Clean up the polluted environment and remove the effects of pollution to the satisfaction
of the Authority.
18
(3) Without prejudice to the provisions of subsections (1) (2) of this section, the court may direct
the polluter to meet the cost of the pollution to any third parties through adequate compensation,
restoration or restitution.”
It is thus evident that there exists an elaborate legal framework governing the exploitation of the
environment and water resources. The National Water Quality Management Strategy 2012 –
2016 in view of the pollution challenges facing the rivers in Kenya proposes the enforcement and
enhancement of environmental guidelines and rules and regulations for the protection of rivers
and lakes. Thus implementation of the existing laws to the letter will go a long way in preserving
our rivers and the environment for today and for the future generations.
19
Chapter Three
3 RESEARCH METHODOLOGY
3.1 The study area
The Narok District has diversified topography, which ranges from a plateau with altitudes
ranging from 1000 m-2350 M.A.S.L at the Southern parts to mountainous landscape ranging to
about 3098 M.A.S.L at the highest peak of Mau escarpment in the North.
The district has five agro-climatic zones namely humid, sub-humid, semi-humid to arid and
semi-arid. Two-thirds of the district is classified as semi-arid. The agro-ecological zones found
in the district include: Tropical Alpine, Upper Highland zones, Lower Highland zones and
upper-midland zones.
The district experiences bi-modal pattern of rainfall with long rains (Mid-March – June) and
short rains (September-November). The amount of rainfall is influenced by bi-annual passage of
Inter-Tropical Convergence Zone (ITCZ). Rainfall distribution is uneven with high potential
areas receiving the highest amount of rainfall ranging from 1200 mm – 1800 mm p.a. while the
lower and drier areas classified as semi-arid receiving 500 mm or less p.a.
The district experiences a wide variation of temperatures throughout the year with mean annual
temperatures varying from 10oC in Mau escarpment to about 20o C in the lower drier areas.
The main water catchments are Ewaso Nyiro South drainage area, and Lake Victoria South
drainage area. Ewaso Nyiro South is the drainage system of rivers emerging from part of Mau
towers and draining into Lake Natron and comprises Rivers: Enkare Narok, Ewaso Nyiro,
Siyiapei and its tributary Enkare Ngoshor.
Flow measurements done along the major Rivers indicate decline in water quantity. This is
mainly due to water catchment destruction and increased human settlement. Vegetation
destruction and illegal logging have also contributed largely to water catchment destruction.
Almost all the open water sources are polluted by bacteria. Periodic physical / chemical analyses
indicate high turbidity levels in most of the surface waters. The main course of water pollution is
siltation (top soil erosion) as a result of destruction of vegetation cover, poor farming methods
near riverbanks, effluent discharge from Narok Town and some tourist facilities in Maasai Mara,
agro-chemical use – (aerial spraying) and leaching of fertilizers into water sources. (Source;
NDEAP, 2009-2013)
20
3.2 Sampling
Sampling was done at four stations namely S1, S2, S3, and S4 running along the river. These
sampling were chosen in such a way that they would capture the change in the water quality as it
flowed through the town. S1was located upstream before the river interacts with the town while
S4 lay downstream at a point where the river ceases to interact with the town directly.
The first sampling was carried out on 17th February 2015 during a wet season while the second
sampling was done on 1st April 2015 after a dry period.
The temperature of the water and general observations was done in situ while the rest of the
water quality parameters were tested in the Public Health Engineering Laboratory.
The samples were transported in clean airtight bottles and refrigerated at 4oC to inhibit any
biological activity.
Care was taken to comply with the WHO water quality monitoring guidelines.
Fig. 3 The sampling points
21
3.3 Limitations of the study
The scope of this study was limited to the change of the water quality due to the influence of the
existence of the town. Therefore sampling was done along the river at and within the town
boundaries. Sampling was done twice due to financial and time constraints.
3.4 Laboratory Examination of Samples
For each sample of water taken from the chosen sampling points, the following parameters were
measured to determine the quality of the river water. They are as follows:
1. pH
2. Temperature
3. Electrical Conductivity
4. Biochemical Oxygen Demand (BOD)
5. Chemical Oxygen Demand (COD)
6. Dissolved Oxygen (DO)
7. Bacteriological examination (Plate count method)
8. Nitrates
9. Iron
10. Turbidity
11. Total solids
3.4.1 pH
pH also known as hydrogen ion concentration refers to the acidity or the basicity of water. It is a
measure of the relative amount of free hydrogen ions in water on a scale of 0 to 14. A pH of 7 is
considered neutral, while that greater than 7 is considered basic. A pH of less than 7 is acidic.
For surface water systems, pH ranges from 6.5 – 8.5. If the water is acidic (pH<6.5), its corrosive
effect can lead to leaching of metal ions such as iron, manganese, copper, lead, and zinc from
the aquifer, plumbing fixtures, and piping thus contain elevated levels of toxic metals. This can
in turn lead to premature damages in the piping system as well as aesthetic problems such as
metallic/sour taste and staining of laundry. On the other hand, water with high alkalinity
(pH>8.5) could indicate that the water is hard which poses the following aesthetic problems:
formation of scale on piping and fixtures causing water pressure and interior diameter of piping
22
to decrease; alkali taste to the water, and difficulty in forming lather with soap. It also decreases
the efficiency of electrical heaters. (Water Research center, 2014).
Apparatus:
pH meter
Procedure:
The pH meter was first calibrated.
Approximately 75 ml of the sample was placed in a 100 ml beaker. The electrodes of the pH
meter were then raised carefully out of the beaker and rinsed in distilled water after which they
were immersed in the beaker containing the sample.
The selector switch was then turned switched to ‘pH’ and the pH reading taken directly from the
meter and recorded.
The selector switch was then turned to ‘CHECK’ and the electrodes carefully raised from the
beaker, rinsed in distilled water and returned to the beaker of distilled water awaiting the next
test.
3.4.2 Temperature:
Temperature of water has a great impact on biological activity and growth. For instance, fish,
insects, zooplankton, phytoplankton and other aquatic species have a preferred temperature range
beyond which decrease and finally die. (USGS water science school, 2014) Similarly, water
temperature affects the amount of oxygen which can dissolve in the water which is key to
survival of aquatic life. The higher the water temperature the less the amount of dissolved
oxygen it can hold.
High water temperature also increases the rate of chemical reactions, for instance, ground water
with high temperature can dissolve more minerals from rocks and thus have a higher electrical
conductivity.
The temperature of rivers and streams is largely controlled by seasonal changes in air
temperatures. However, there are other factors that have an effect on air temperature such as:
Lack of riparian plants which serve to shade the water and keep its temperature down
Sedimentation: the sediments absorb heat rays hence increasing the temperature of the
surrounding water
Low flows whereby the dry river bed absorbs more heat and retains it for long. When the water
covers these beds again, the temperature of the water is substantially raised.
23
A change in water temperature from the natural levels is termed as thermal pollution.
Apparatus:
Thermometer
Procedure:
Temperature of the river water was measured on site by inserting the thermometer at each of the
four sampling points. The readings were recorded accordingly.
3.4.3 Electrical Conductivity (Specific Conductivity):
This is the measure of the ability of water to conduct an electrical current. Electrical conductivity
is dependent on the amount of dissolved inorganic solids in water such as chlorides, sodium,
calcium, etc., thus it gives an estimate of the same. For instance, pure water has low conductivity
as compared with sea water. Similarly, rain water has high conductivity due to dissolved gases
and dust in the air.
The conductivity of a river is principally determined by the geological conditions and the soils of
the catchment through which it flows. For instance, rivers flowing through catchments with
rocks such as granite will have low conductivity, while those with rocks such as limestone and
clay soils will have high conductivity.
The conductivity of a river will tend to remain within a specified range. However an increase in
conductivity over time can be an indication of pollution. Industrial pollution and urban runoff are
characterized by high conductivity.
The temperature of water influences conductivity, increase in temperature increases conductivity.
Therefore conductivity is measured at a standard temperature of 25oC.
Apparatus:
a. Conductivity meter
Procedure:
The conductivity meter was calibrated and rinsed with distilled water. It was then dipped into
each of the samples one at a time and the conductivity readings taken in µs
24
3.4.4 Biochemical Oxygen Demand (BOD)
Apparatus:
a. Burettes
b. Pipettes
c. BOD bottles
Reagents for dilution water:
a. Phosphate buffer solution
b. Ferric chloride solution
c. Magnesium sulphate solution
d. Calcium chloride solution
Reagents for dissolved oxygen determination by Azide modification of Winkler Method:
a. Manganous sulphate solution
b. Concentrated sulphuric acid
c. Starch indicator solution
d. Standard sodium thiosulphate solution 0.025N
Procedure:
6 litres of dilution water were made up by adding 6 ml of each of the following reagents to 6
litres of distilled water kept aerated in the aspirator bottle: phosphate buffer solution, ferric
chloride solution, magnesium Sulphate solution, and calcium chloride solution. They were well
mixed as the aeration continued.
For each sample, the following volumes were measured: 2.8ml, 5.6ml, 11.2ml, and 28ml; and
placed in different BOD bottles with a capacity of 280ml and then filled with dilution water
(without overflowing or trapping air bubbles) such that the resulting dilutions were in the ratios
1:10, 1:25, 1:50, and 1:100 respectively.
Two such sets were prepared for each sample.
Similarly, two BOD bottles, one for each set, were filled with dilution water without the sample
and labelled as blanks.
25
For each sample, one set of the prepared samples was placed in the incubation cabinet and
incubated at 20oC for 5 days. The other set was tested for dissolved oxygen concentration by the
Azide modification of the Winkler method as follows:
1. For each bottle, the stopper was removed and 2ml of manganous sulphate and alkali
azide-iodide solutions added in quick succession. The stopper was then replaced ensuring
no air bubbles were trapped.
2. The contents of the bottle were then mixed through inverting the bottle several times and
letting the precipitate settle halfway down the bottle. The contents were then mixed again
and left to settle as before.
3. 2ml of concentrated sulphuric acid were then added to the contents of the bottle, the
stopper replaced and the contents mixed till all the precipitate had dissolved.
4. 203 ml were measured from the bottle and transferred to an Erlenmeyer flask and titrated
against standard sodium thiosulphate solution till there was a colour change to pale
yellow. 1ml of starch solution was then added to the titrant and the titration continued till
the blue colour disappeared.
The above procedure was repeated for the incubated samples after 5 days of incubation.
The dissolved oxygen (mg/l) was reported as the volume (ml) of the titrant used.
3.4.5 Chemical Oxygen Demand (COD)
Apparatus:
a. Reflux apparatus with ground glass joint
b. 250ml Erlenmeyer flask with ground glass joints
c. Glass beads
d. Pipettes
Reagents:
a. Distilled water
b. Standard potassium dichromate solution (0.25N)
c. Concentrated sulphuric acid reagent containing silver sulphate
d. Standard ferrous ammonium sulphate solution 0.025N
26
e. Powdered mercuric sulphate
f. Phenathroline ferrous sulphate solution (ferroin indicator)
Procedure:
0.4g of solid mercuric sulphate, 20 ml of sample, 10ml of 0.25N potassium dichromate and a few
glass beads were added into a 250ml Erlenmeyer flask. This was done for each sample and a
blank sample prepared as such but with 20 ml of distilled water in place of the sample.
The five flasks were then fitted to the condenser system ensuring that the glass joint was snug.
The flow of cooling water was then started. 30ml of silver sulphate concentrated sulphuric acid
solution was added slowly to each flask through the open end of the condenser and the flask
contents mixed through swirling while adding the acid.
The heaters were then switched on and refluxed for two hours.
The condensers were rinsed with distilled water and the flasks removed from the heater after
disconnecting the condenser. The contents of the flasks were then diluted with distilled water to
about 150ml and mixed.
3 drops of ferroin indicator solution were added to the flask and the contents titrated against
standard ferrous ammonium sulphate solution of 0.1N strength. The end point of the titration was
a colour change from blue-green to reddish-brown.
3.4.6 Dissolved Oxygen (DO)
Apparatus:
a. D.O. bottles with stoppers
b. Pipette
c. Erlenmeyer flask
Reagents:
a. Manganous sulphate solution
b. Alkali azide iodide solution
c. Concentrated sulphuric acid
d. Starch indicator solution
e. Standard sodium thiosulphate solution, 0.025N
27
Procedure:
The samples were placed in the DO bottles ensuring that no air was trapped. A fifth DO bottle
was filled with distilled water and acted as control for the experiment.
To each bottle, the stopper was removed and the 2ml of manganous sulphate solution and alkali
azide iodide solution were added in quick succession and the stopper carefully replaced. The
contents were mixed several times and the precipitate allowed to settle halfway. They were then
mixed again and the precipitate allowed to settle halfway for the second time.
2ml of concentrated sulphuric acid was added to each bottle, the stopper replaced and the
contents mixed again until all the precipitate dissolved.
203ml was measured from the bottle and transferred to an Erlenmeyer flask and titrated against
standard sodium thiosulphate solution till the colour changed to pale yellow. 1ml of starch
indicator solution was then added and titration continued till the blue colour disappeared. This
was done for each sample and the blank. The dissolved oxygen concentration in mg/l was
reported as the ml of titrant used.
3.4.7 Total Coliform counts
The term “total coliforms” refers to a large group of Gram-negative, rod-shaped bacteria that
share several characteristics. The group includes thermo-tolerant coliforms and bacteria of fecal
origin, as well as some bacteria that may be isolated from environmental sources. Thus the
presence of total coliforms may or may not indicate fecal contamination.
In extreme cases, a high count for the total coliform group may be associated with a low, or even
zero, count for thermo-tolerant coliforms. Such a result would not necessarily indicate the
presence of fecal contamination. It might be caused by entry of soil or organic matter into the
water or by conditions suitable for the growth of other types of coliform.
In the laboratory total coliforms are grown in or on a medium containing lactose, at a
temperature of 37 °C. They are provisionally identified by the production of acid and gas from
the fermentation of lactose. (Bartam Jamie et al, WHO 1992)
The total coliform counts was performed using the multiple tube fermentation using three tubes
each containing 10ml 1ml and 0.1ml of sample. A presumptive test was first carried out using
lauryl tryptose broth. The positives were identified and by presence of gas in the inoculated tubes
and colour change from purple to yellow. The positives proceeded to the confirmatory test whose
media is brilliant green lactose bile broth. The positives from the confirmatory test were then
used together with a standard statistical table of the most probable number (MPN) per 100ml.
(see standard methods for examination of water and waste water 14th Edition)
28
3.4.8 Nitrates
Apparatus
a. Lovibond comparator
b. Test tubes
Reagents
a. Brucine reagent
b. Conc. Sulphuric acid
Procedure:
1ml of sample was placed in a test tube and 1ml of Brucine reagent added followed by 2ml of
concentrated sulphuric acid. After about 7 minutes, readings were taken from the lovibond
comparator. This was done by matching the test tube content’s colour to that of the lovibond
comparator’s disk. The disk reading gives the concentration of nitrates in mg/L
3.4.9 Iron
Apparatus:
a. Separating funnel
b. Lovibond comparator
c. Disc no. 3/11
Reagents:
a. Dilute hydrochloric acid
b. Potassium permanganate solution
c. Amyl acetate alcoholic solution
d. Ammonium thiocyanate solution
Procedure:
For each sample, 5ml of it, 1ml hydrochloric acid and two drops of potassium permanganate
solution were added in that order and mixed. 5ml of ammonium thiocyanate solution was then
added to the funnel followed by 10ml of amyl acetate alcoholic solution and the mixture shaken
vigorously.
29
It was then allowed to settle and the lower aqueous layer discarded while the upper layer was
transferred to the comparator cell. The above procedure was repeated using distilled water in
place of the sample which was labelled as a blank and placed on the left hand side of the
comparator. The colour produced was then matched against the standard disc.
The amount of iron (mg/l) in the sample was reported as disc reading x 200
3.4.10 Turbidity
Apparatus:
a. Clean cell sample
b. Cell riser
c. 2100A turbidimeter
Procedure:
The turbid meter was switched on and allowed to warm up for some time. 30ml of the sample
was placed in a clean sample cell. Upon comparison with the sample, the standard which had its
turbidity closest and greater than that of the sample was chosen as that in the range 100-1000
FTU, and the cell riser was inserted into the cell holder assembly and the instrument
standardized.
The sample was then placed into the cell holder as well as the light shield and the turbidity value
read off. This was repeated for all the samples.
3.4.11 Solids
Apparatus:
a. Evaporating dish
b. Filter paper
c. Desiccator
d. Suction pump
e. Evaporating dish
f. Analytical balance
g. Drying oven
30
Procedure:
a. Suspended solids
A filter paper was weighed and its weight recorded. It was then wet and placed in a suction pump
where 100ml of sample was placed and the suction pump switched on. After all the sample had
passed, the filter paper was transferred to the oven. After drying the filter paper was transferred
to a desiccator and later weighed again. The weight of the suspended solids was calculated as the
difference between the weight after drying and the initial weight of the filter paper.
b. Dissolved solids
An evaporating dish was weighed and its initial weight recorded. The filtrate left from procedure
(a) was then placed in an evaporating dish. The dish was put in a water bath where evaporation
took place. After evaporation, the weight of the dish and its contents was taken again. The
weight of the dissolved solids was calculated as the difference between the final and initial
weight of the dish.
For both suspended and dissolved solids, the concentration in mg/l was calculated as:
𝑤𝑒𝑖𝑔ℎ𝑡 × 100
100 × 10−3𝑚𝑔/𝑙
Total solids = suspended solids + dissolved solids
31
Chapter Four
4 RESULTS AND ANALYSIS First sampling: 17th Feb 2015 – Wet period (W)
Second sampling: 1st April 2015 – Dry period (D)
Parameter
Sampling Points
S1 S2 S3 S4
W D W D W D W D
pH 6.75 7.84 6.70 7.80 6.76 7.82 6.80 7.83
Temperature(oC) 21 23 19 23 19 23 21 23
Electrical Conductivity (µs) 190 390 201 430 255 628 260 576
COD (mg/l) 64 52 48 56 144 48 96 36
DO (mg/l) 6.7 5.9 6.3 5.9 6.5 3.6 6.4 5.2
Nitrates(mg/l) 4.0 1.0 3.0 1.0 3.0 1.0 2.0 2.0
Iron (mg/l) 2.0 0.4 1.6 0.4 1.6 0.4 1.6 0.4
Turbidity (FTU) 235 130 240 140 248 135 245 140
BOD (mg/l) <20 29.2 <20 18.2 <20 41.2 <20 48.7
Total coliform counts (MPN
index/100ml)
11 43 7 7 93 210 21 150
Total suspended solids
(mg/l)
1800 500 1300 400 1000 300 1200 200
Total dissolved solids (mg/l) 350 160 200 210 470 570 410 630
Total solids (mg/l) 2150 660 1500 610 1470 870 1610 830
32
4.1 pH:
Sampling points pH reading
Wet period Dry period
S1 6.75 7.84
S2 6.70 7.80
S3 6.76 7.82
S4 6.80 7.83
The pH of the river was relatively constant across the four sampling stations averaging at about
6.75 during the wet season and about 7.82 during the dry season. This pH range suggests that
the river is capable of supporting aquatic life which thrives at a pH range of 6.5 – 9.0. A decrease
in pH value during the wet season can be attributed to the influence of storm water from the
town.
4.1.1 Temperature
Sampling points Temperature (oC)
Wet period Dry period
S1 21 23
S2 19 23
S3 19 23
S4 21 23
The temperature was also relatively constant across the four sampling stations averaging at 20oC
in the wet period and 23oC in the dry season. The small temperature variation confirms that
there exist no sources of thermal pollution within the town’s vicinity.
Similarly, presence of trees along the banks of the river provided shade which facilitated in
maintaining relatively low temperature.
33
4.1.2 Electrical conductivity
Sampling points Electrical Conductivity (µs)
Wet Period Dry period
S1 190 390
S2 201 430
S3 255 628
S4 260 576
The electrical conductivity of the river increased downstream across all the four sampling
stations in both the wet and dry periods. The high values recorded during the dry period are due
to the following reasons:
a. Electrical conductivity measures the amount of dissolved inorganic substances in the
water. During the dry period, the river was less diluted per unit volume as compared to
the wet season, thus more dissolved substances per unit volume. This relationship is
exhibited in the increase in total dissolved solids from the wet period to the dry period.
b. The increase in temperature in the dry period contributed to the high conductivity
values as conductivity is proportional to temperature.
34
4.1.3 BOD
Sampling points BOD (mg/l)
Wet period Dry period
S1 <20 29.2
S2 <20 18.2
S3 <20 41.2
S4 <20 48.7
Wet period
The biochemical oxygen demand for the river in all the points sampled was found to be less than
20mg/l. This was due to the fact that the dissolved oxygen depletion after five days of incubation
was less than 2mg/l for all the samples. The BOD blank had an acceptable dissolved oxygen
depletion of 0.2mg/l which suggests that the river water was ‘weak’ in BOD. I.e. the amount of
oxygen required by bacteria to break down the organic matter in the river water was less than
2mg/l after a five day incubation period which suggests minimal amounts of organic matter in
the river.
190 201
255 260
390
430
628
576
0
100
200
300
400
500
600
700
1 2 3 4
Elec
tric
al C
on
du
ctiv
ity
(µs)
Sampling Points
Electrical Conductivity (µs)
Wet period
Dry period
35
This is despite the fact that main drain from the town emptied into the river just upstream of
sampling station S3, which had no significant impacts on the BOD results for station S3.
Similarly the fact that the river was found to be weak in BOD in spite of the input of excreta
from the Maasai livestock when they came to drink from the river suggests that the self-
purification mechanism of the river was very effective.
The low BOD5 can be attributed to the dilution of river water by the high rainfall experienced in
the rainy season.
Dry Period
The BOD5 values during the dry period were higher than those recorded in the wet period. The
values also varied downstream with the sampling points S3 and S4 recording the highest values
of 41.2mg/l and 48.7mg/l respectively. This is attributed to the point source pollution just
upstream of S3 which drains most of the town.
The BOD5 of the river was higher in the dry period than in the wet period. This can be attributed
to the river being less diluted per unit volume hence more concentration of organic matter per
unit volume as compared to the situation during the wet period.
It was also observed that for high levels of dissolved oxygen such as during the wet period, the
BOD5 was low and was high for low levels of dissolved oxygen.
4.1.4 COD
Sampling points COD (mg/l)
Wet period Dry period
S1 64 52
S2 48 56
S3 144 48
S4 96 36
Wet period:
The chemical oxygen demand is seen to vary downstream with the highest value (144mg/l) being
at sampling station S3 which is just below the point where the town’s main drain empties into the
river. The fact that the BOD at the same point is relatively low (about 20mg/l) and approximately
14% of the COD suggests that the waste released from the town contains more non-
biodegradable matter but which is chemically oxidized.
36
The value of the COD at sampling point S4 which is downstream of S3 shows a COD value of
96mg/l which is about 67% of that point S3. This suggests that the effluent from the town is
being more and more diluted as it continues to mix with the river water in spite of having two car
wash stations between sampling point S3 and S4.
Dry period:
The COD values are relatively low which can be attributed to reduced loads expended into the
river.
4.1.5 DO
Sampling points DO (mg/l)
Wet period Dry period
S1 6.7 5.9
S2 6.3 5.9
S3 6.5 3.6
S4 6.4 5.2
64
48
144
96
5256
48
36
0
20
40
60
80
100
120
140
160
1 2 3 4
CO
D (
mg/
l)
Sampling Points
COD (mg/l)
Wet Period
Dry period
37
The dissolved oxygen was relatively lower in the dry period. This can be attributed to the
following reasons:
a. During the dry season, the temperature of the water was relatively higher. The solubility
of oxygen in water decreases with increase in temperature hence the low DO values.
b. During the wet season, the river flows with a lot of turbulence due to increased volume
caused by storm water and runoff. The turbulence causes the river to dissolve more
oxygen thus the higher DO values in the wet period. In the dry season, the river flow is
slower with little turbulence thus less oxygen dissolves.
It is observed that more oxygen was being consumed at around sampling station S3. This can be
attributed to the presence of the town drain just upstream of the station which introduces organic
and inorganic load to the river for which oxygen is consumed in its stabilization.
6.76.3
6.5 6.4
5.9 5.9
3.6
5.2
0
1
2
3
4
5
6
7
8
1 2 3 4
Dis
solv
ed O
xyge
n (
mg/
l)
Sampling Points
DO (mg/l)
Wet period
Dry period
38
4.1.6 Total Coliform counts
Sampling points Total coliform counts (/100ml) MPN index
Wet period Dry period
S1 11 43
S2 7 7
S3 93 210
S4 21 150
The dry period recorded particularly high values of coliform counts as compared with the wet
period. This can be attributed to the fact that during the dry period, the river is less diluted per
unit volume, hence more concentration of coliforms.
Sampling point S3 recorded the highest number of the coliforms in both the wet and dry periods
owing to the fact that the station is located just downstream of the drain through which the town
effluent enters the river.
11 7
93
21
43
7
210
150
0
50
100
150
200
250
1 2 3 4
Tota
l Co
lifo
rm c
ou
nts
(/1
00
ml)
Samplng Points
Total Coliform Counts
Wet Period
Dry Period
39
4.1.7 Nitrates
Sampling points Nitrates (mg/l)
Wet period Dry period
S1 4.0 1.0
S2 3.0 1.0
S3 3.0 1.0
S4 2.0 2.0
Soil naturally contains organic matter which contains nitrogen compounds. Similarly, river water
will naturally contain ammonia from excreta by aquatic organisms and aquatic plants. This
ammonia is converted by bacteria into nitrates hence the presence of nitrates even in the dry
period.
The level of nitrates in the river was higher in the wet season than during the dry season. The
high levels of nitrates are attributed to agricultural activities which make use of nitrogenous
fertilizers. The nitrogenous compounds are converted by nitrifying bacteria into nitrates which
are then washed into the river during the rainy season.
4
3 3
2
1 1 1
2
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
1 2 3 4
Nit
rate
s (m
g/l)
Sampling Points
Nitrates (mg/l)
Wet period
Dry period
40
4.1.8 Iron
Sampling points Iron (mg/l)
Wet period Dry period
S1 2.0 0.4
S2 1.6 0.4
S3 1.6 0.4
S4 1.6 0.4
The soils in the Narok north area are well drained moderately deep to very deep dark brown,
friable and slightly smeary clay loam to clay; ando – luvic phaeozems. The soils in the Mau
region where the river has its origins are well drained, shallow, dark reddish brown to dark
brown, friable to firm sandy clay loam and in places, rocky. They belong to the class of chromo-
luvic phaeozems, lithic phase with rock outcrops. (Jaetzold Ralph, et al, 2009)
The reddish brown, dark brown colour of these soils is characteristic of iron oxides which
explain the high iron content in the river during the wet season as runoff washes the soil into the
river.
The iron content in the river was substantially low in the dry period and represents the naturally
occurring iron in rivers.
2
1.6 1.6 1.6
0.4 0.4 0.4 0.4
0
0.5
1
1.5
2
2.5
1 2 3 4
Iro
n (
mg/
l)
Samplig Points
Iron (mg/l)
Wet period
Dry period
41
4.1.9 Turbidity
Sampling points Turbidity reading (FTU)
Wet period Dry period
S1 235 130
S2 240 140
S3 248 135
S4 245 140
Turbidity in the wet period was much turbid as compared to the dry period averaging at 242
FTU. This is attributed to the influx of eroded soil into the river. Similarly, in the wet period,
there was increased turbulence in the river as storm water and runoff joins it.
The dry period recorded lower values of turbidity averaging at 136 FTU.
235 240248 245
130140 135 140
0
50
100
150
200
250
300
1 2 3 4
Turb
idit
y (F
TU)
Sampling Points
Turbidity (FTU)
Wet period
Dry period
42
4.1.10 Total Solids
Sampling
points
Suspended solids (mg/l) Dissolved solids (mg/l) Total solids (mg/l)
Wet period Dry period Wet period Dry period Wet period Dry period
S1 1800 500 350 160 2150 660
S2 1300 400 200 210 1500 610
S3 1000 300 470 570 1470 870
S4 1200 200 410 630 1610 830
The suspend solids were higher in the wet period due to the influx of eroded soils and other town
wastes carried by storm water into the river. This is the case with the total solids. However the
dissolved solids were more in the dry period than in the wet period which can be attributed to the
raised temperature which enhances solubility.
0
200
400
600
800
1000
1200
1400
1600
1800
2000
1 2 3 4
Tota
l Su
spe
nd
ed
So
lids
()m
g/l
Sampling Points
Total Suspended Solids (mg/l)
Wet Period
Dry Period
43
0
100
200
300
400
500
600
700
1 2 3 4
Tota
l Dis
solv
ed
So
lids
(mg/
l)
Sampling Points
Total Dissolved Solids (mg/l)
Wet Period
Dry Period
0
500
1000
1500
2000
2500
1 2 3 4
Tota
l So
lids
g/l
Sampling points
Total Solids (mg/l)
Wet Period
Dry Period
44
4.2 The Pollution Profile
The sampling stations were distributed along the river with S1 as the most upstream point while
S4 was the most downstream point. The stations S2 and S3 lie between these points.
Below is a comparison of the quality of the river water as it enters the town (S1) and as it leaves
the town (S4) which gives an idea of how much the town pollutes the river with respect to the
sampled stations.
Parameter Sampling Stations % change in
quality (S1 vs
S4)
Mean
S1 S4
Wet
Period
Dry
Period
Wet
Period
Dry
Period
Wet
Period
Dry
Period
pH 6.75 7.84 6.80 7.83 +0.74 -0.13 +0.305
Temperature(oC) 21 23 21 23 +9.5 0.00 +4.75
Electrical
Conductivity (µs)
190 390 260 576 +36.8
+47.69
+42.25
COD (mg/l) 64 52 96 36 +50.0 -30.77 +9.62
DO (mg/l) 6.7 5.9 6.4 5.2 -4.48 -11.86 -8.17
Nitrates(mg/l) 4.0 1.0 2.0 2.0 -50.0 +100.00 +25.0
Iron (mg/l) 2.0 0.4 1.6 0.4 -20.0 +0.00 -10.0
Turbidity (FTU) 235 130 245 140 +4.26 +7.69 5.85
BOD (mg/l) <20 29.2 <20 48.7 0.0 +66.78 +33.39
Total coliform counts
(MPN /100 ml)
11 43 21 150 +90.1
+248.84
+169.47
Total suspended
solids (mg/l)
1800 500 1200 200 -33.3
-60.00
-46.5
Total dissolved solids
(mg/l)
350 160 410 630 +17.1
+293.75
+155.43
45
A notable change in the quality of the river water was established as it flows from station S1
through S2 and S3 to station S4. For instance, the dissolved oxygen decreases by about 8.17% by
the time the river passes through the town. This suggests pollution by organic matter and that
which is chemically oxidized thereby using up dissolved oxygen.
The BOD and total coliform count increases by 33.39% and 169.47% indicating a probable
pollution organic in nature.
The graph below summarizes how the various water quality parameters change as the river flows
through the town.
46
Key to x-axis parameters:
1. pH
2. Temperature(oC)
3. Electrical Conductivity (µs)
4. COD (mg/l)
5. DO (mg/l)
6. Nitrates(mg/l)
7. Iron (mg/l)
8. Turbidity (FTU)
9. BOD (mg/l)
10. Total coliform counts (MPN /100 ml)
11. Total suspended solids (mg/l)
12. Total dissolved solids (mg/l)
-60
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Ave
rage
ch
ange
in Q
ual
ity
%
Parameters
% change in river quality from S1 to S4
47
0
10
20
30
40
50
60
Comparison of water quality at sampling stations S1 and S4 (Wet Period)
S1
S2
48
0
10
20
30
40
50
60
Comparison of Water quality at sampling stations S1 and S4 (Dry Period)
S1
S4
49
A point source pollution area was noted just upstream of station S3 caused by a drain that pours
the town’s waste and storm water into the river. This point source pollution has major influence
in the water quality of station S3. Below is a comparison between the qualities of water at S3 and
the EMCWQR 2006 limits for effluent discharge into aquatic environments.
Parameter Sampling Station S3 EMCWQR
2006 discharge
to aquatic
environment
limits
Wet
Period
Dry
Period
Mean
pH 6.76 7.82 7.29 6.5-8.5
Temperature(oC) 19 23
21
± 3 above
ambient temp.
Electrical Conductivity
(µs)
255 628
441.5
-
COD (mg/l) 144 48 96 50
DO (mg/l) 6.5 3.6 5.05 -
Nitrates(mg/l) 3.0 1.0 2 100
Iron (mg/l) 1.6 0.4 1 10
Turbidity (FTU) 248 135 191.5 -
BOD (mg/l) <20 41.2 30.6 30
Total coliform counts
(MPN /100 ml)
93 210
151.5
30
Total suspended solids
(mg/l)
1000 300
650
30
Total dissolved solids
(mg/l)
470 570
520
1200
50
Analysis of the main source of pollution of the river, i.e. the point source pollution gives the
following observations:
a. The pH, temperature, nitrates and iron levels are within the acceptable limits provided for
by the EMCWQR 2006.
b. However, the COD, BOD, total coliform counts and total suspended solids levels are
beyond the acceptable limits provided for by the EMCWQR 2006. This indicates that this
point source pollution introduces mainly organic load and wastes from agricultural uses
of water.
51
Chapter Five
5 CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusion:
A successful examination of the water quality monitoring variables was carried out on the
Enkare Narok River. The variables tested are: pH, temperature, electric conductivity, BOD,
COD, DO, Total coliform counts, iron, nitrates, turbidity, total suspended solids and total
dissolved solids. From these tests, the following conclusions were arrived at:
1. A point source pollution was identified just upstream of sampling station S3 and which
was largely responsible for the introduction of organic load, storm water and urban runoff
into the river. This explains the high values of BOD, COD, total coliform counts and total
suspended solids experienced at S3 as well as low values of DO downstream. This point
is the major source of pollution.
2. The level of pollution in the river was quite low since there was neither bad odor nor
color change in the river water experienced during sampling. Similarly the water quality
parameters such as BOD exceeded the EMCWQR 2006 limits slightly i.e. by 0.6mg/l.
3. The Narok area is prone to erosion during the rainy season. This was established by the
high values of iron content of up to 2mg/l recorded in the wet period. The dark reddish
brown to dark brown loamy clay soils of Narok contain iron oxides which are introduced
to the river with the eroded soils.
4. The Enkare Narok River becomes more polluted in the dry period than during the wet
period. This means it is more prone to cause water borne diseases in the dry period hence
more caution is needed then in the usage of the river water.
52
5.2 Recommendations:
1. Construction of a sewerage system in Narok town, complete with a sewage treatment
plant to avert any chance of introducing raw sewage to the river and to streamline waste
disposal and management. Currently there exists no sewerage system in the town and
exhaust services are used for the septic tanks in use. The exhauster services dump their
contents to abandoned quarries outside the town which poses a threat of contaminating
ground water.
2. Construction of a dam to collect storm water which can then be treated and used by the
town residents. This will reduce amount of load introduced to the river and will offer an
additional source of water for the residents.
3. Implementation of laws and regulations governing the protection of water resources and
the environment. In Narok town, structures are built up to the river bank (<30m from the
river bank) posing high threat of pollution to the river and at the same time interfering
with the setup of the river ecosystem. Similarly, car wash enterprises exist at the banks of
the river hence posing a threat to its health.
4. Construction of watering troughs for the Maasai livestock away from the river to prevent
them from releasing their excreta into the river.
5. Implementation of soil erosion prevention measures such as terraced farming,
afforestation and reforestation to reduce silting in the river.
6. Public sensitization and participation in conservation of the river.
53
6 REFERENCES [1] APHA (1975) Standard Methods for the examination of water and waste water 14th Ed.
Washington DC
[2] Bartram Jamie, Balance Richard, (1996) Water Quality Monitoring - A Practical Guide to the
Design and Implementation of Freshwater UNEP/WHO
[3] Department of Water Resources; National Water Quality management strategy 2012-2016
Ministry of Water Resources (http://www.water.go.ke/downloads/NWQMS.pdf )
[4] Environmental Management and Coordination Water Quality Regulations, 2006
[5] Institute of Economic Affairs (June, 2007), A rapid assessment of Kenya’s water sanitation
and sewerage framework, Nairobi
[6] Jaetzold Ralph et al (2009) Farm Management Handbook Of Kenya Vol. II Annex: - Atlas of
Agro - Ecological Zones, Soils and Fertilizing by Group of Districts in Southern Rift Valley -
Subpart B1a Narok County Ministry of Agriculture, Kenya, in Cooperation with the German
Agency for Technical Cooperation (GTZ)
[7] Klein, Louis (1966) River Pollution v2 Causes and Effects Butterworth London
[8] NEMA, Narok District Environmental Action Plan 2009 – 2013
(http://www.nema.go.ke/index.php?option=com_phocadownload&view=category&download=3
69:narokpdf&id=94:neap-reports)
[9] P.G. Whitehead, Lack T, (1982) Dispersion and self-purification of pollutants in surface
water systems A report by IHP working group 6.1. UNESCO
[10] Radojevic M, Bashkin VN (1999). Practical Environmental Analysis, Cambridge, U.K.
Royal Society of Chemist
[11] The Environmental Management And Co-Ordination Act, 1999 no 8 Of 1999
(http://www.nema.go.ke/images/documents/emca.pdf)
[12] UNESCO (2009) The World Water Development Report 3 ‘Water in a changing world’
[13] UN Water (2015), Report on the Achievements during the International Decade for Action
Water for Life 2005-2015 Germany (http://www.ais.unwater.org/water-for-life-
decadereport/Water-for-Life-DecadeReport_WEB.pdf )
[14] United States Geological Survey Water science school
http://water.usgs.gov/edu/waterquality.html (retreived February 2015)
[15] Water Act 2002 (http://www.wrma.or.ke/images/jdownloads/wateract2002.pdf)
54
7 APPENDICES:
7.1 Appendix 1
Table 1: Quality Standards for Sources of Domestic Water
Parameter Guide Value (Max allowable)
pH 6.5 – 8.5
Suspended solids 30 (mg/L)
Nitrate - NO3 10 (mg/L)
Ammonia – NH3 0.5 (mg/L)
Nitrite – NO2 3 (mg/L)
Total Dissolved Solids 1200 (mg/L)
E. coli Nil/100ml
Fluoride 1.5 (mg/L)
Phenols Nil (mg/L)
Arsenic 0.01 (mg/L)
Cadmium 0.01 (mg/L)
Lead 0.05 (mg/L)
Selenium 0.01 (mg/L)
Copper 0.05 (mg/L)
Zinc 1.5 (mg/L)
Alkyl benzyl sulphonates 0.5 (mg/L)
Permanganate value (PV) 1.0 (mg/L)
Nil means less than limit of detection using prescribed sampling and analytical methods and
equipment as determined by the Authority (NEMA).
55
Table 2: Standards for Effluent Discharge into the Environment
Parameter Max Allowable (limits)
1,1,1-trichloroethane (mg/l) 3
1,1,2-trichloethane (mg/l) 0.06
1,1-dichloroethylene 0.2
1,2-dichloroethane 0.04
1,3-dichloropropene (mg/l) 0.02
Alkyl Mercury compounds Nd
Ammonia, ammonium compounds, NO3 compounds and NO2
compounds (Sum total of ammonia-N times 4 plus nitrate-N and
Nitrite-N) (mg/l)
100
Arsenic (mg/l) 0.02
Arsenic and its compounds (mg/l) 0.1
Benzene (mg/l) 0.1
Biochemical Oxygen Demand (BOD 5days at 20oC) (mg/l) 30
Boron (mg/l) 1.0
Boron and its compounds – non marine (mg/l) 10
Boron and its compounds –marine (mg/l) 30
Cadmium (mg/l) 0.01
Cadmium and its compounds (mg/l) 0.1
Carbon tetrachloride 0.02
Chemical Oxygen Demand (COD (mg/l) 50
Chromium VI (mg/l) 0.05
Chloride (mg/l) 250
Chlorine free residue 0.10
56
Chromium total 2
cis –1,2- dichloro ethylene 0.4
Copper (mg/l) 1.0
Dichloromethane (mg/l) 0.2
Dissolved iron (mg/l) 10
Dissolved Manganese(mg/l) 10
E.coli (Counts / 100 ml) Nil
Fluoride (mg/l) 1.5
Fluoride and its compounds (marine and non-marine) (mg/l) 8
Lead (mg/l) 0.01
Lead and its compounds (mg/l) 0.1
n-Hexane extracts (animal and vegetable fats) (mg/l) 30
n-Hexane extracts (mineral oil) (mg/l) 5
Oil and grease Nil
Organo-Phosphorus compounds (parathion,methyl parathion,methyl
demeton and Ethyl parantrophenyl phenylphosphorothroate, EPN
only) (mg/l)
1.0
Polychlorinated biphenyls, PCBs (mg/l) 0.003
pH ( Hydrogen ion activity----marine) 5.0-9.0
pH ( Hydrogen ion activity--non marine) 6.5-8.5
Phenols (mg/l) 0.001
Selenium (mg/l) 0.01
Selenium and its compounds (mg/l) 0.1
Hexavalent Chromium VI compounds (mg/l) 0.5
Sulphide (mg/l) 0.1
57
Simazine (mg/l) 0.03
Total Suspended Solids, (mg/l) 30
Tetrachloroethylene (mg/l) 0.1
Thiobencarb (mg/l) 0.1
Temperature (in degrees celious) based on ambient temperature ± 3
Thiram (mg/l) 0.06
Total coliforms ( counts /100 ml) 30
Total Cyanogen (mg/l) Nd
Total Nickel (mg/l) 0.3
Total Dissolved solids (mg/l) 1200
Colour in Hazen Units (H.U) 15
Detergents (mg/l) Nil
Total mercury (mg/l) 0.005
Trichloroethylene (mg/l) 0.3
Zinc (mg/l) 0.5
Whole effluent toxicity
Total Phosphorus (mg/l) 2 Guideline value
Total Nitrogen 2 Guideline value
And any other parameters as may be prescribed by the Authority (NEMA) from time to
time
Remarks
Standard values are daily/monthly average discharge values. Not detectable (Nd) means that the
pollution status is below the detectable level by the measurement methods established by the
Authority
58
Table 3: Microbiological Quality Guidelines for Wastewater Use in Irrigation
Reuse conditions Exposed group Intestinal
nematodes
(MPN/L)*
Coliforms
(MPN/100 ml)
Unrestricted
irrigation ( crops
likely to be eaten
uncooked, sports
fields, public parks)
Workers, consumers,
public
<1 <1000**
Restricted irrigation
(cereal crops,
industrial crops,
fodder crops, pasture
and trees***
Workers <1 No standard
recommended
* Ascaris lumbricoides, Trichuris trichiura and human hookworms.
** A more stringent guideline (<200 coliform group of bacteria per 100 ml) is appropriate for
public lawns, such as hotel lawns, with which the public may come into direct contact.
*** In the case of fruit trees, irrigation should cease two weeks before fruit is picked and fruit
should be picked off the ground. Overhead irrigation should not be used
Table 4: Standards for Irrigation Water
Parameter
Permissible Level
pH 6.5-8.5
Aluminium 5 (mg/L)
Arsenic 0.1 (mg/L)
Boron 0.1 (mg/L)
Cadmium 0.5 (mg/L)
Chloride 0.01 (mg/L)
59
Chromium 1.5 (mg/L)
Cobalt 0.1 (mg/L)
Copper 0.05 (mg/L)
E.coli Nil/100 ml
Fluoride 1.0 (mg/L)
Iron 1 (mg/L)
Lead 5 (mg/L)
Selenium 0.19 (mg/L)
Sodium Absorption Ratio (SAR) 6 (mg/L)
Total Dissolved Solids 1200 (mg/L)
Zinc 2 (mg/L)
And any other parameters as may be prescribed by the Authority (NEMA) from time to time
Table 5: Quality Standards for Recreational Waters
Parameter Maximum Permissible Level
Arsenic (mg/l) 0.05
Fecal coliform (Counts/100 ml) Nil
Total coliform (Counts/100 ml) 500
Cadmium 0.01
Chromium 0.1
Colour (True Colour Units) 100
Light Penetration (meters) 1.2
Mercury (mg/L) 0.001
Odour (Threshold Odour Number, TON) 16
60
Oil and Grease (mg/L) 5
pH 6 – 9
Radiation, Total (Bq/L) 0.37
Surfactant, MBAs (mg/L) 2
Temperature (0C) 30
Turbidity (NTU) 50
And any other parameters as may be prescribed by the Authority (NEMA) from time to time
61
7.2 Appendix 2 Plates
Plate 1 Plate 2
Plate 3 Plate 4
Plate 1 – 3: an abandoned quarry where raw sewage from septic tanks in the town is dumped.
Plate 4: an exhauster services vehicle heading to the abandoned quarry to empty its contents.
Plate 5 Plate 6
Car wash activities along the river Maasai cattle coming from the river for a drink
62
Plate 7
A dried up lagoon where sewage from
septic tanks was being dumped about 10
years ago
Plate 8 Plate 9
Plate 8 – 10: a view of the drain that
empties the town’s effluents and
storm water to the river. This was
identified as the point source
pollution.
Plate 10
63
Plate 11: Temperature measurement at sampling station S1