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