JOMO KENYATTA UNIVERSITY

OF

AGRICULTURE AND TECHNOLOGY

DEPARTMENT OF CIVIL, CONSTRUCTION AND ENVIRONMENTAL

ENGINEERING

FINAL YEAR PROJECT REPORT

TITLE:

POLLUTION PROFILE IN A RIVER CROSSING A TOWN:

CASE STUDY OF RIVER RUIRU IN RUIRU TOWN

AUTHOR:

OCHIENG S. SYLVESTER

E25-0112/04

SUPERVISOR

Dr. G. M. THUMBI

A Project submitted in partial fulfillment of the award of BSc. Civil, Construction and Environmental Engineering of the

Jomo Kenyatta University of Agriculture and Technology

E25-0112/04 i OCHIENG S. (2010)

DECLARATION

“I Ochieng S. Sylvester do solemnly declare that this report is my original

work and to the best of my knowledge, it has not been submitted for any

degree award in any University or Institution.”

Signed……………………………… (Author)

Date……….………………………..

E25-0112/04

CERTIFICATION

“I have read this report and approve it for examination.”

Signed……………………………………… (Supervisor)

Date………….……………………………..

Dr. G. M. THUMBI

E25-0112/04 ii OCHIENG S. (2010)

DEDICATION

I dedicate this project to my parents and siblings who have been there for me

through countless ups and downs and who have always had been there for me.

To my future wife and kids, this is for you too, and to my friends who have

encouraged me throughout the whole course, my classmates and my

supervisor, this is for you all.

“In the end, you're measured not by how much you undertake but by what you finally

accomplish.”

Donald Trump

E25-0112/04 iii OCHIENG S. (2010)

ACKNOWLEDGEMENT

The following have contributed in one way or the other in making this Project a

success.

My project supervisor, Dr. Thumbi for guiding and advising me through the whole

period

The Civil Engineering department for technical and material support throughout the

entire project period

Mr. Mwaura who gave me vital insights necessary for the project

I am highly indebted to Mr. Munyi and Mr. Karugu for their technical support in the

environmental laboratory throughout my practical sessions

My classmates for their friendship and assistance

To all my friends, who have in one way or another contributed to the completion of

this project

I am entirely grateful to you all for your support

E25-0112/04 iv OCHIENG S. (2010)

LIST OF TABLES

Table 1: Collected data

Table 2: Average values for the respective sampling stations

Table 3: Kenya standards for water for use

Table 4: World Health Organization standards for water

Table 5: European standards for water

Table 6: budget for the whole project

Table 7: schedule for the project duration

LIST OF FIGURES

Fig 1: Google maps Kenya showing Ruiru town and its environs.

Fig 2: temperature variations for the four sampling stations

Fig 3: hydrogen ion concentration (ph) for the four sampling stations

Fig 4: dissolved oxygen concentrations for the four sampling stations

Fig 5: chemical oxygen demand concentrations for the four sampling stations

Fig 6: ammonia concentration variations for the four sampling stations

Fig 7: variations of the averages of the parameters tested with relation to the sampling

stations

E25-0112/04 v OCHIENG S. (2010)

LIST OF PLATES

Plate 1; a man washing his clothes after bathing in the Ruiru River

Plate 2; direct effluent discharge into Ruiru River located behind the Henkel chemical

industry

Plate 3; Photo adapted from Google maps Kenya showing the entire study area and

the location of the sampling stations.

Plate 4: the water fall section near Thika road

Plate 5: Google earth image of the section showing the river crossing under Thika

road

Plate 6: sampling point for station 2, dry period.

Plate 7: the researcher taking samples at sampling station 2, wet period

Plate 8: stagnant and polluted section of the river

Plate 9: the researcher collecting samples from station 3

Plate 10: car washing in the river; one of the sources of pollution in the river

Plate 11: the researcher testing samples in the University laboratory

LIST OF ABBREVIATIONS

COD Chemical Oxygen Demand

DO Dissolved Oxygen

BOD5 Biochemical Oxygen Demand

pH Hydrogen ion concentration

DDT Dichlorodiphenyltrichloroethane

Mg/L milligrams per liter

E25-0112/04 vi OCHIENG S. (2010)

TABLE OF CONTENTS

DECLARATION........................................................................................................... i

DEDICATION ............................................................................................................. ii

ACKNOWLEDGEMENT ........................................................................................... iii

LIST OF TABLES ...................................................................................................... iv

LIST OF FIGURES ..................................................................................................... iv

LIST OF PLATES ........................................................................................................ v

LIST OF ABBREVIATIONS ...................................................................................... v

TABLE OF CONTENTS ............................................................................................ vi

ABSTRACT ................................................................................................................ ix

CHAPTER 1 ............................................................................................................ - 1 -

INTRODUCTION ................................................................................................... - 1 -

1.1 BACKGROUND .................................................................................... - 2 -

1.2 STUDY JUSTIFICATION ..................................................................... - 3 -

1.3 PROBLEM STATEMENT ..................................................................... - 5 -

1.4 RESEARCH OBJECTIVES ................................................................... - 5 -

1.4.1 Main objective: ................................................................................ - 5 -

1.4.2 Specific objectives ........................................................................... - 5 -

1.5 RESEARCH HYPOTHESIS .................................................................. - 5 -

1.6 STUDY LIMITATIONS. ....................................................................... - 5 -

CHAPTER 2 ............................................................................................................ - 6 -

LITERATURE REVIEW ........................................................................................ - 6 -

2.1 INTRODUCTION .................................................................................. - 6 -

2.2 TYPES OF POLLUTANTS ................................................................... - 7 -

2.3 SOURCES OF POLLUTANTS .............................................................. - 8 -

2.3.1 Municipal Wastes............................................................................. - 8 -

2.3.2 Industrial Wastes .............................................................................. - 9 -

2.3.3 Agricultural wastes ........................................................................ - 10 -

2.3.4 Storm water .................................................................................... - 10 -

2.4 EFFECTS OF WATER POLLUTION ................................................. - 11 -

2.5 SELF-PURIFICATION OF STREAMS ............................................... - 12 -

2.6 DESCRIPTION OF SOME POLLUTION PARAMETERS ................ - 13 -

2.6.1 Temperature ................................................................................... - 13 -

E25-0112/04 vii OCHIENG S. (2010)

2.6.2 Chemical Oxygen Demand (COD) ................................................ - 13 -

2.6.3 Dissolved Oxygen (DO) ................................................................ - 14 -

2.6.4 Hydrogen ion concentration (pH) .................................................. - 14 -

2.6.5 Ammonia ....................................................................................... - 14 -

CHAPTER 3 .......................................................................................................... - 15 -

RESEARCH METHODOLOGY .......................................................................... - 15 -

3.1 STUDY AREA ..................................................................................... - 15 -

3.2 SAMPLING STATIONS ...................................................................... - 16 -

3.3 SAMPLING .......................................................................................... - 17 -

3.4 CATCHMENT CHARACTERISTICS ................................................ - 17 -

3.5 LABORATORY EXAMINATION OF WATER ................................. - 19 -

CHAPTER 4 .......................................................................................................... - 20 -

RESULTS AND DISCUSSION ........................................................................... - 20 -

4.2 DATA COLLECTED/RESULTS ......................................................... - 20 -

4.3 AVERAGES ......................................................................................... - 21 -

4.4 DATA ANALYSIS ......................................................................... - 22 -

4.4.1 Temperature ................................................................................... - 22 -

4.4.2 Hydrogen ion concentration ........................................................... - 23 -

4.4.3 Dissolved Oxygen .......................................................................... - 24 -

4.4.4 Chemical Oxygen Demand ............................................................ - 25 -

4.4.5 Ammonia ....................................................................................... - 26 -

4.4.6 Averages ........................................................................................ - 27 -

4.4.7 Pollution Profile ............................................................................. - 28 -

4.5 Discussion ....................................................................................... - 29 -

CHAPTER 5 .......................................................................................................... - 30 -

CONCLUSIONS AND RECOMMENDATIONS ................................................ - 30 -

5.1 CONCLUSIONS .................................................................................. - 30 -

5.2 RECOMMENDATIONS ...................................................................... - 31 -

BIBLIOGRAPHY/REFERENCES ....................................................................... - 33 -

APPENDIX ........................................................................................................... - 34 -

APPENDIX 1: BUDGET ...................................................................................... - 34 -

APPENDIX 2: SCHEDULE ................................................................................. - 34 -

APPENDIX 3: TABLES OF STANDARDS ........................................................ - 35 -

E25-0112/04 viii OCHIENG S. (2010)

APPENDIX 3.1: Kenya standards .......................................................... - 35 -

APPENDIX 3.2: World Health Organization Standards ........................ - 35 -

APPENDIX 3.3: European Standards ..................................................... - 35 -

APPENDIX 4: PROCEDURES ............................................................................ - 36 -

4.1 Temperature .......................................................................................... - 36 -

4.2 COD (Open Reflux Method) ................................................................ - 36 -

Reagents: ................................................................................................. - 36 -

Apparatus: ............................................................................................... - 36 -

Procedure: ............................................................................................... - 37 -

Calculations: ........................................................................................... - 37 -

4.3 Dissolved Oxygen (DO), Titration Method .......................................... - 38 -

Introduction: ............................................................................................ - 38 -

Reagents: ................................................................................................. - 38 -

Procedure ................................................................................................ - 38 -

Calculations: ........................................................................................... - 38 -

4.4 Hydrogen Ion Concentration or pH (Using The pH Meter Method.) ... - 39 -

Procedure ................................................................................................ - 39 -

4.5 Ammonia Test (DPD Method).............................................................. - 39 -

Apparatus ................................................................................................ - 39 -

Reagents .................................................................................................. - 39 -

Procedure ................................................................................................ - 39 -

APPENDIX 5 : PLATES ...................................................................................... - 40 -

E25-0112/04 ix OCHIENG S. (2010)

ABSTRACT

The industrial revolution has brought with it substantial benefits to mankind, but at

the same time it has instigated negative impacts on the environment. The casualties

have been air, soil and water among others, which are being polluted at alarming

rates. The focus of the study was on water pollution, with an emphasis on rivers that

flow through urban areas. Rivers that traverse towns, cities and other urban centers

have been great casualties since they are mostly used to discard most of the wastes.

The study aimed to use laboratory tests and procedures to determine whether River

Ruiru is polluted as it flows through Ruiru town.

The parameters tested in the research process included the standard water quality

variables such as chemical oxygen demand (COD), biochemical oxygen demand

(BOD), and ammonia, environmental variables Dissolved Oxygen (DO), Temperature

and hydrogen concentration (pH). A case study of River Ruiru was used to determine

whether indeed the pollution profile of the river changes as it flows through Ruiru

town. The data was collected from four sampling stations selected as representative of

the flow characteristics and pollution profile of the river.

The values obtained were then compared against those recommended by the various

standardization organizations to determine whether they fall within the recommended

values. The pH values ranged from 7.25 to 8.27 which were within the recommended

values of between 6.5 and 8.5. The maximum ammonia concentration recommended

is 0.5mg/L; however the ammonia concentrations went as high as 1.33mg/L with the

lowest value being 0.55mg/L. These are much higher than the recommended values.

The recommended dissolved oxygen concentration is at least 5.0mg/L, the specimen

concentrations were well below this value, ranging between 2.1 and 4.4. The

recommended maximum chemical oxygen demand concentration is 50g/L, however

the river sample concentration went as high as 335mg/L with the lowest

concentration being 155mg/L.

These results indicate that the river is therefore polluted as it flows through the town,

especially since the values increase as the river progresses towards the town exit.

Conclusions and recommendations were then made on the way forward in mitigating

the pollution of the river.

E25-0112/04 - 1 - OCHIENG S. (2010)

CHAPTER 1

INTRODUCTION

In most developing countries, point and non-point source pollution are major

environmental problems affecting water quality. The situation is exacerbated by

inadequate treatment for domestic wastes and poor agricultural practices. In East

Africa, land use changes caused by rapid urbanization and clearance of forests to

create room for agriculture have emerged as major stressors of streams and rivers. In

Kenya, degraded water quality, losses of biodiversity and altered hydrography have

been recorded among streams and rivers draining urban areas. On the other hand,

deforestation and cultivation have been found to cause an increase in water

temperature, conductivity, total suspended and dissolved solids and turbidity. Animal

overuse on the riparian areas has been found to increase ammonia and nitrite as a

consequence of increased run-off of animal wastes into streams.

Near-stream human activities like sand mining, bathing, (see plate 1) laundry and row

crop agriculture have been reported to cause the greatest influence on stream habitat

and biotic characteristics, (Wandiga, S., 1999).

Plate 1; a man washing his clothes after bathing in River Ruiru

E25-0112/04 - 2 - OCHIENG S. (2010)

1.1 BACKGROUND

Pollution of rivers which exists today in the world actually began in the 19th Century

with the coming of the Industrial Revolution and the resulting phenomenal growth of

population in developing countries. The problem was further intensified by the

establishment of factories on the banks of rivers where the water was freely available

for power and for manufacturing processes. Thus large quantities of liquid, solid and

sewage wastes find their way into the rivers.

Fish, which was formerly abundant, disappeared and water supplies became

endangered. Kenya, a third world country in the East African region had a population

of about 31 million according to the 1999 census, (Wikipedia).

The rapid growth in population has placed great pressure on housing especially in

urban areas and services such as health, water and education. This is due to increasing

levels of poverty and unemployment, poor general sanitation, environmental

degradation, and insecurity which remain a major concern for Ruiru. This has led to a

definite disposal of solid and liquid wastes into the streams and rivers running though

these areas. For town and city residents, potable water supply by relevant authorities

is less than 60% and most people use the water directly without prior treatment.

Against this backdrop, increased intensity of agriculture and deforestation coupled

with the rapid growth of urban centers and industrial activities pose a potential threat

in degrading small streams and rivers. Because of their urban set up these small

ecosystems are often not protected by buffer zones that allow for the absorption of

immense run-off from Jua Kali sheds and settlements on the riparian areas,

(Wandiga, S., 1999).

The problem is worsened by the fact that most industries and malfunctional sewerage

facilities discharge directly into the small streams and rivers. This has consequently

led to sedimentation and eutrophication that have affected domestic and industrial

water supply. Ruiru is a town located in Thika District of Kenya‟s Central Province.

It is located within three kilometers of Nairobi's city boundary, Ruiru is a dormitory

town for the Kenya's capital city, and is connected by both railway line as well as a

road network. The town covers an area of approximately 292 km², and is surrounded

by numerous coffee plantations. According to the 1999 census, Ruiru town had a

population of 100,000, but has since undergone a rapid population growth as a result

E25-0112/04 - 3 - OCHIENG S. (2010)

Plate 2; direct effluent discharge into Ruiru River

located behind the Henkel chemical industry

of the shortage of available housing in Nairobi. A 2005 estimate put the town‟s

population at over 220,000. The town has struggled to adapt to the influx of people

and social amenities such as schools, health centers, and waste disposal systems have

been put under pressure, (Wikipedia).

Nine rivers flow through Nairobi city and its surroundings. There should be enough

water for its three million residents. However, years of unchecked pollution have

turned them into death traps flowing with poison. Ruiru River, which is part of the

Nairobi river basin, is highly polluted with waste from industries, sewage from

domestic settings and runoff from agricultural areas. As a result of pollution, very

little or no aquatic life exists along the river. Water from the river is no longer

available for domestic and agricultural use. By mitigation of pollution through

policies and public awareness, a number of benefits can be realized from the Ruiru

River such as a source of clean water for domestic, agricultural and industrial use and

a source of fish which can supplement the food in the country. The overall effect

would be the improvement of the lives of the town and city residents, (K. V. Ellis,

1989).

1.2 STUDY JUSTIFICATION

Worldwide, more than one billion people lack access to safe drinking water. At the

end of the 20th century an estimated 80 per cent of the Earth‟s urban residents did not

have adequate potable-

water supplies. Only a very

small quantity of the Earth‟s

fresh water, around 0.008

per cent, is currently

available for human use.

Seventy per cent of that

goes to agriculture, 23 per

cent to industry, and only 8

per cent to domestic

consumption. At the same

time, demand for fresh water is rapidly rising. In developing countries, 95 per cent of

human waste water is discharged untreated into nearby rivers (see plate 2) that are

E25-0112/04 - 4 - OCHIENG S. (2010)

frequently also sources of drinking water. People who drink such water are likely to

get infected with water-borne diseases, the foremost health problem in the developing

world. Sewage pollution also kills freshwater fish, an important food source, and

leads to deleterious algae blooms in coastal areas. The amount, variability, and

reliability of water flow in rivers have enormous significance for plants, animals, and

people living along the course of the river. Rivers and their flood plains possess

diverse and valuable ecosystems. Not only is the availability of fresh water in itself

vital to sustaining life, but it also supports lush vegetation and abundant insect life

that form the base of the food chain. In the river channel fish feed on the plants and

insects and are themselves eaten by birds, amphibians, reptiles, and mammals. Away

from the channel, wetlands maintained by seepage and occasionally flooded by the

river support rich and diverse habitats that are important not only for resident species,

but also for migrating birds and animals that use wetlands as staging posts while

moving seasonally between different homes (domiciles), (Wandiga, S., 1999).

River (riparian) ecosystems are some of the most important in nature and they depend

entirely on the regime of the river for their existence. Hence, great care must be

exercised when altering this regime through basin and river management, as careless

handling or over-exploitation of water resources has catastrophic impacts on riparian

ecosystems. Despite rivers‟ importance, Ruiru residents have been unforgiving;

destroying what was once a source of fresh drinking water. In the 1990s, people could

fish in some of the rivers, some of which are now choked with weeds and dangerous

chemicals. Conservationists say if these rivers were cleaned up, their waters would

significantly help in the attainment of Millennium Development Goals set by the

United Nations. People would have enough clean water, diseases would reduce,

bringing down health bills, and people would in turn have more money to improve

their livelihoods. This study is meant to examine the quality of water and pollution in

general along the river profile at selected points of the river. The study is meant to

focus on current pollution levels of Ruiru River and highlight how pollution changes

along the profile of the river. From this, it is hoped that it will be possible to

determine whether Ruiru town has an influence on the river, (Wandiga, S., 1999).

E25-0112/04 - 5 - OCHIENG S. (2010)

1.3 PROBLEM STATEMENT

Pollution along Ruiru River is at critical levels. Previous studies done by various

environmental groups, has shown that there is urgency to restore the river to its

natural state. Population growth has sharply increased demand for freshwater. The

much needed water can be sourced from the river if it is clean. The residential areas

surrounding the river, but do not have access to potable water for domestic use can

benefit greatly from this river if it is restored to a clean state. This study is meant to

determine whether Ruiru town is responsible for polluting the river and if so, what

can be done about it.

1.4 RESEARCH OBJECTIVES

1.4.1 Main objective:

The main objective is to evaluate the pollution profile of River Ruiru as it flows

through Ruiru town.

1.4.2 Specific objectives

To evaluate the organic levels at different points along the river.

To determine the effluent discharge points from Ruiru town.

1.5 RESEARCH HYPOTHESIS

Most Rivers flowing through urban centers get polluted by wastes, based on that fact,

it is therefore hypothesized that River Ruiru is polluted as it flows through Ruiru

town.

1.6 STUDY LIMITATIONS.

The research will be limited to selected points along the river. These points will be

carefully selected to give a picture of how pollution changes along the profile of the

river. This is due to limited time assigned to the project. Due to limited financing,

only selected areas can be studied within a limited budget and as such an extensive

study of the whole river is not possible.

E25-0112/04 - 6 - OCHIENG S. (2010)

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

A river is a natural stream of water, usually freshwater, flowing toward an ocean, a

lake, or another stream. In some cases a river may flow underground or dry up

completely before reaching another body of water. Usually larger streams are called

rivers while smaller streams are called creeks, brooks, rivulets, rills, and many other

terms, (Wikipedia). The great majority of rivers eventually discharge into either the

sea or a lake, although some rivers disappear due to water loss through seepage into

the ground and evaporation into the air. Rivers have long been used, and abused, for

the disposal of human, agricultural and industrial waste (effluent). Through their

natural flow and ecology rivers have the capacity to cleanse themselves and they can

cope with surprisingly large amounts of effluent. However, any river has a finite

capacity to digest sewage and absorb fertilizers washing from crop lands, (Microsoft

Encarta).

If this capacity is exceeded, over-abundant bacteria, algae, and plant life consume all

the oxygen dissolved in the water (Eutrophication),suffocating insect and fish life,

and leading to the destruction of the entire riparian ecosystem through disruption of

the food chain, (Microsoft Encarta).Rivers and lakes, being formed from water which

has percolated through the surface soil will contain dissolved salts, traces of organic

matter, suspended matter, and such dissolved gases as oxygen, nitrogen and carbon

dioxide. The Human activities, however, may lead to alterations in the natural

composition of river water. Man‟s pollution of the air adds to the chemical

composition of the rainwater (acid rain).Run off from fields and gardens often carry

nutrients and pollutants from fertilizers, pesticides and animal wastes. Effluents

which man adds to river and other waterways have a direct effect on the hydrologic

cycle, (Microsoft Encarta).

E25-0112/04 - 7 - OCHIENG S. (2010)

2.2 TYPES OF POLLUTANTS

The main types of pollutants of rivers include:

Sewage and other oxygen-demanding wastes

These are largely carbonaceous organic material, the decomposition of which

leads to oxygen depletion. These include raw sewage discharged directly to a

river.

Pesticides and herbicides.

Chemicals used to kill unwanted pests, insects and weeds on farms may be

collected by rainwater runoff and carried into streams, especially if these

substances are applied too lavishly. Some of these chemicals are biodegradable

and quickly decay harmless or less harmful forms, while others are non-

biodegradable and remain dangerous for a long time. Substances such as DDT

(Dichlorodiphenyltrichloroethane) are absorbed into tissues of animals and are

passes on the food chain increasing the concentration of the pollutants. Animals

at the top of the food chain may suffer cancers, reproductive problems and death.

Infectious agents (pathogens). Many disease causing organisms that are present in

small numbers in most natural waters are considered pollutants when found in

drinking water. Such parasites as Giardia lamblia and Cryptspridiumparvum

occasionally turn up in urban water supplies. These parasites can cause illness

especially in people who are old or very young, and in people who are already

suffering from other diseases. In 1993 an outbreak of Cryptspridium in the water

supply of Milwaukee, Wisconsin, sickened more than 400,000 people and killed

more than 100.

Plant nutrients that can stimulate the growth of aquatic plants, which then

interfere with water uses and, when decaying, deplete the dissolved oxygen and

produce disagreeable odors.

Petroleum, especially from oil spills.

Inorganic minerals and chemical compounds.

Sediments consisting of soil and mineral particles washed by storms and flood

water from croplands, unprotected soils, mine workings, roads, and bulldozed

urban areas. They can also be pollutants if it is present in large amounts. Soil

erosions produced by the removal of soil-trapping trees near waterways, or

carried by rainwater and floodwater from croplands, strip mines, and roads, can

damage a stream or lake by introducing too much nutrient matter. This leads to

E25-0112/04 - 8 - OCHIENG S. (2010)

eutrophication. Sedimentation can also cover streambed gravel in which many

fish, such as salmon and trout, lay their eggs.

Radioactive substances from the wastes of uranium and thorium mining and

refining, from nuclear power plants, and from the industrial, medical, and

scientific use of radioactive materials. Thermal Pollution Thermal pollution is a

temperature change in natural water bodies caused by human influence. The

temperature change can be upwards or downwards. In the Northern Hemisphere,

a common cause of thermal pollution is the use of water as a coolant, especially

in power plants. Water used as a coolant is returned to the natural environment at

a higher temperature. Increases in water temperature can impact on aquatic

organisms by;

Decreasing oxygen supply

Killing fish juveniles which are vulnerable to small increases in temperature

Affecting ecosystem composition.

In the Southern Hemisphere, thermal pollution is commonly caused by the release of

very cold water from the base of reservoirs, with severe effects on fish (particularly

eggs and larvae), macro invertebrates and river productivity. Temperature may be the

most important single factor affecting the occurrence and behavior of life in surface

water. It affects practically every physical factor that is of concern in water quality

management in that it alters the density, viscosity, vapor pressure, surface tension,

gas solubility and the rate of gas diffusion. It also affects the rate of all chemical and

biological reactions, (K. V. Ellis, 1989).

2.3 SOURCES OF POLLUTANTS

The major sources of water pollution can be classified as municipal, industrial,

agricultural and storm water.

2.3.1 Municipal Wastes

Municipal water pollution consists of wastewater from homes and commercial

establishments. For many years, the main goal of municipal sewage disposal was

simply to reduce its content of suspended solids, oxygen-demanding materials,

dissolved inorganic compounds (particularly compounds of phosphorus and

nitrogen), and harmful bacteria. The Royal Commission on Sewage Disposal has

recommended that in order to avoid nuisance, sewage effluent should have a

biochemical oxygen demand (BOD5) of not more than 20ppm and a suspended solids

E25-0112/04 - 9 - OCHIENG S. (2010)

content of not greater than 30ppm where the dilution with the river water is at least

eightfold. In recent years, however, more stress has been placed on improving the

means of disposal of the solid residues from municipal treatment processes.

The basic methods of treating municipal wastewater fall into three stages;

1. Primary treatment, including grit removal, screening, grinding,

flocculation(aggregation of the solids), and sedimentation;

2. Secondary treatment, which entails oxidation of dissolved organic matter by

means of biologically active sludge, which is then filtered off;

3. Tertiary treatment, in which advanced biological methods of nitrogen

removal and chemical and physical methods such as granular filtration and

activated carbon adsorption are employed.

The handling and disposal of solid residues can account for 25 to 50 per cent of the

capital and operational costs of a treatment plant, (Wandiga, S., 1999).

2.3.2 Industrial Wastes

The characteristics of industrial wastewaters can differ markedly both within and

among industries. The impact of industrial discharges depends not only on their

collective characteristics, such as biochemical oxygen demand and the amount of

suspended solids, but also on their content of specific inorganic and organic

substances. Three options (which are not mutually exclusive) are available in

controlling industrial wastewater;

1. Control can take place at the point of generation within the plant;

2. Wastewater can be pretreated for discharge to municipal treatment systems;

3. Wastewater can be treated completely at the plant and either reused or

discharged directly into the receiving waters.

Even if the effluent is treated by the best practicable means and is satisfactory on the

basis of certain arbitrary standards, any waste effluent into a stream cannot be as good

as the natural river water. Industrial waste is a major contributor of chemical

pollution, (Microsoft Encarta).

E25-0112/04 - 10 - OCHIENG S. (2010)

2.3.3 Agricultural wastes

Agriculture, including commercial livestock and poultry farming, is the source of

many organic and inorganic pollutants in surface waters and groundwater. These

contaminants include both sediment from the erosion of cropland and compounds of

phosphorus and nitrogen that partly originate in animal wastes and commercial

fertilizers. Animal wastes are high in oxygen-demanding material, nitrogen, and

phosphorus, and they often harbor pathogenic organisms. Wastes from commercial

feeders are contained and disposed of on land; their main threat to natural waters,

therefore, is via run-off and leaching. When farmland is tilled and bare soil is

revealed, rainwater carries billions of tons of topsoil into waterways each year,

causing loss of valuable topsoil and adding sediment to produce turbidity in surface

waters, (Microsoft Encarta).

The other context of agricultural issues involves the transport of agricultural

chemicals (nitrates, phosphates, pesticides, herbicides etc.) via surface runoff. This

result occurs when chemical use is excessive or poorly timed with respect to high

precipitation. The resulting contaminated runoff represents not only a waste of

agricultural chemicals, but also an environmental threat to downstream ecosystems.

The alternative to conventional farming is organic farming which eliminates or

greatly reduces chemical usage. Control may involve settling basins for liquids,

limited biological treatment in aerobic or anaerobic lagoons, and a variety of other

methods, (Microsoft Encarta).

2.3.4 Storm water

Storm water is a term used to describe water that originates during precipitation

events. It may also be used to apply to water that originates with snowmelt or runoff

water from overwatering that enters the storm water system. Storm water that does

not soak into the ground becomes surface runoff, which either flows into surface

waterways or is channeled into storm sewers. Storm water is of concern for two main

issues: one related to the volume and timing of runoff water (flood control and water

supplies) and the other related to potential contaminants that the water is carrying, i.e.

water pollution. Because impervious surfaces (parking lots, roads, buildings,

compacted soil) do not allow rain to infiltrate into the ground, more runoff is

generated than in the undeveloped condition, (Microsoft Encarta).

E25-0112/04 - 11 - OCHIENG S. (2010)

The additional runoff can erode watercourses (streams and rivers) as well as cause

flooding when the storm water collection system is overwhelmed by the additional

flow. Because the water is flushed out of the watershed during the storm event, little

infiltrates the soil, replenishes groundwater, or supplies stream base flow in dry

weather. In addition to delivering higher pollutants from the urban catchment

increased storm water flow can lead to stream erosion, encourage weed invasion and

can alter natural flow regimes which native species rely on for a range for activities

including spawning, juvenile development and migration, (Wandiga, S., 1999).

2.4 EFFECTS OF WATER POLLUTION

1. Notable effects of water pollution include those involved in human health.

Nitrates (the salts of nitric acid) in drinking water can cause a disease in infants

that sometimes results in death. Cadmium in sludge-derived fertilizer can be

absorbed by crops; if ingested in sufficient amounts, the metal can cause an acute

diarrhea disorder and liver and kidney damage. The hazardous nature of inorganic

substances such as mercury, arsenic, and lead has long been known or strongly

suspected. Lakes are especially vulnerable to pollution. One problem,

eutrophication, occurs when lake water becomes artificially enriched with

nutrients, causing abnormal plant growth. Run-off of chemical fertilizer from

cultivated fields may trigger this. The process of eutrophication can produce

aesthetic problems such as bad tastes and odors and unsightly green scum of

algae, as well as dense growth of rooted plants, oxygen depletion in the deeper

waters and bottom sediments of lakes, and other chemical changes such as

precipitation of calcium carbonate in hard waters.

2. Another problem, of growing concern in recent years, is acid rain, which has left

many lakes in northern and Eastern Europe and north-eastern North America

totally devoid of life. Eutrophication may perhaps best be described as increased

lake productivity resulting from an increased loading of nutrient material which

has not been balanced by an equivalent release of these nutrients materials in the

outflow, (K. V. Ellis, 1989).

3. It was once assumed that lakes became naturally more eutrophic through time.

However, evidence strongly indicates that most recent changes are due to the

increase in nutrients coming from the land in consequence of human activities

(such as forest clearance, ploughing and fertilizing). This increase caused by

human beings is known as anthropogenic eutrophication. The supply of dissolved

E25-0112/04 - 12 - OCHIENG S. (2010)

phosphorus to lakes and rivers is greatly increased by domestic and industrial

sewage disposal, unless steps are taken to remove it from the final effluent.

Polyphosphate-based detergents may also contribute a significant proportion. As

the turbidity of water (its murkiness, caused by suspended nutrients) increases so

does the production of phytoplankton: greater rates of bacterial decomposition

remove dissolved oxygen from deep water faster than it can be replaced from the

atmosphere ,leaving less of the water habitable for fish.

4. Eutrophication can cause massive growth of aquatic plants due to high supply of

nutrients. Eutrophication can be reversed by cutting back the phosphorus loads,

either by diversion from sensitive waters or by chemical precipitation with iron

salts (“phosphate stripping”) at such point-sources as the effluents of sewage-

works. Shallow lakes take longer to restore because they recycle phosphorus

much more efficiently than deep lakes, and methods to stimulate alternative food

webs (“bio-manipulation”) are used to overcome the symptoms of eutrophication.

Where nutrient sources are diffuse and difficult to control, the use of artificial

mixing systems can be considered as a means to reduce algal growth, (K. V. Ellis,

1989).

2.5 SELF-PURIFICATION OF STREAMS

Self-purification is the sum of those processes which bring a polluted water body

back into its normal original state. Rivers receiving continuous pollution by organic

wastes tend to overcome the pollution load by purifying itself and recover naturally in

the course of time, thus exemplifying the ancient saying that running water purifies

itself. Self-purification of rivers, one of the most remarkable of nature‟s working

leading to the eventual elimination of the organic pollution is dependent on

biochemical reactions brought about by the activities of micro-organisms which give

sufficient dissolved oxygen, utilize the organic matter as food and break down

complex compounds to simpler and harmless end products.

The river thus recovers naturally from the effects of pollution and is said to have

undergone „self-purification‟. Self-purification is a complicated process and each

river has its own specific capacity for purifying itself which can only be properly

evaluated after an extensive chemical, physical, hydrological and biological survey.

Some rivers are able to undergo self-purification in a fairly short distance; others

require dozens of miles or even more, (K. V. Ellis, 1989).

E25-0112/04 - 13 - OCHIENG S. (2010)

The factors influencing self-purification of a river are:-

Dissolved oxygen

Type of organic matter

Toxic substances

Physical characteristics of a stream

Weather conditions

Dilution

Sedimentation and Sludge deposits

Temperature

2.6 DESCRIPTION OF SOME POLLUTION PARAMETERS

2.6.1 Temperature

Temperature is one of the important parameters in natural surface water systems. The

temperature of surface waters governs to a large extent the biological species present

and their rates of activity. Temperature has an effect on most chemical reactions that

occurs in natural water systems. Oxygen is less soluble in warm water than in cold

water. Temperature also has pronounced effect on solubility of gases in water. High

order species such as fish are affected dramatically by temperature and by dissolved

oxygen levels, which are a function of temperature, (K. V. Ellis, 1989).

2.6.2 Chemical Oxygen Demand (COD)

The chemical oxygen demand (COD) test is a measure of the quantity of oxygen that

is required to oxidize the organic matter in a wastewater sample under specific

conditions of oxidizing agent, temperature and time. During the determination of

COD, organic matter is converted to carbon dioxide and water, amino nitrogen to

ammonia nitrogen and organic nitrogen in higher oxidation states to nitrates

regardless of biological degradability of the substances. COD values should be

greater than BOD values and may be much greater when significant amounts of

biologically resistant organic matter is present. The COD test is used extensively in

the analysis of industrial wastes.

Results may be obtained within a relatively short time (3 hours). In conjunction with

the BOD test, the COD test is helpful in indicating toxic conditions and the presence

of biologically resistant organic substances. The test is widely used in the operation

of treatment facilities because of the speed with which results can be obtained, (K. V.

Ellis, 1989).

E25-0112/04 - 14 - OCHIENG S. (2010)

2.6.3 Dissolved Oxygen (DO)

Surface waters of good quality should be saturated with dissolved oxygen. The

average concentration of dissolved oxygen in water is 6mg/l. A fall in dissolved

oxygen level in water is one of the first indications that organic matter has polluted a

body of water. The dissolved oxygen level in water depends on physical, chemical,

and biological activities prevailing in the water body and thus, it is one of the

important parameters for assessing the purity of the water body. Dissolved oxygen

levels in natural and wastewaters are dependent on the physical, chemical and

biochemical activities prevailing in the water body.

Adequate DO is necessary for the life of the fish and other aquatic organisms. The

DO concentration may also be associated with corrosivity of water, photosynthetic

activity and septicity. The DO is also used in the biochemical oxygen demand

determination, (K. V. Ellis, 1989).

2.6.4 Hydrogen ion concentration (pH)

Pure water is only weakly dissociated into hydrogen and hydroxyl ions (H+ and OH

respectively).Theoretically, pure water contains H+ and OH- each at a concentration

of10-7g ions/l. If the H+ concentration is more than 10-7g ions/l the solution is said

to be acidic; if the H concentration is less than 10-7, it is said to be alkaline. The pH

of a solution is the logarithm (to base 10) of the reciprocal of the hydrogen ion

concentration. PH values less than 7 indicate acidity and pH values greater than

7indicate alkalinity. The pH of most natural water lies between 4 and 9. Many waters

show an alkaline reaction due to presence of carbonate and bicarbonate ions, (K. V.

Ellis, 1989).

2.6.5 Ammonia

Ammonia occurs as a breakdown product of nitrogenous material in natural waters. It

is also found in domestic effluents and certain industrial waste waters. Ammonia is

harmful to fish and other forms of aquatic life especially for ammonia levels greater

than 0.2mg/l, and the ammonia level must be carefully controlled in water used for

fish farms and aquariums. Ammonia test are routinely applied to pollution control on

effluents and waste waters, and for monitoring of drinking water, (K. V. Ellis, 1989).

E25-0112/04 - 15 - OCHIENG S. (2010)

CHAPTER 3

RESEARCH METHODOLOGY

3.1 STUDY AREA

Ruiru River flows through the Ruiru town and it is the main river in the town. It one

of the tributaries of Nairobi River which eventually flows into the Athi River,

ultimately flowing to the Indian Ocean about 600km away. This river is mostly

narrow, shallow and polluted .It is characterized by a brown colour and it has a

waterfall about four meters high about fifty meters away from the busy Thika Road.

After the waterfall, the river disappears under the rocks and what is left on the surface

is a very slender stream that also eventually vanishes underground, (Wikipedia). See

location of Ruiru town and its environs in the Google map figure shown in fig: 1

Fig 1: Google maps showing Ruiru town and its environs

E25-0112/04 - 16 - OCHIENG S. (2010)

Plate 3; Photo adapted from Google maps Kenya showing the entire study area and the

location of the sampling stations.

3.2 SAMPLING STATIONS

A total of four stations were selected for sampling. Since the objective of the study

was to determine if Ruiru town influences the pollution profile of the river, the first

sampling station was taken at the point where the river enters the town, before being

influenced in any way to determine if it was polluted before it entered the town. The

next two stations were taken within the town but at convenient distances apart. The

last sampling station was taken at the river‟s exit from the town. By comparing the

results from the four sampling stations, it was possible to determine from laboratory

tests whether the river was polluted as it flowed through Ruiru town.

The sampling stations are located as shown in the satellite map above, (see plate 3):

Station 1- Entry into Ruiru town

Station 2- Behind Henkel chemical industry

Station 3- Underneath Thika Road bridge

Station 4- Exit of Ruiru town

E25-0112/04 - 17 - OCHIENG S. (2010)

3.3 SAMPLING

Water samples were collected from all the four sampling stations. During the

sampling process, date, time, exact location and temperatures of the samples were

recorded on site. Water samples were collected at right angles to the flow of the

stream on straight stretches of the stream. Samples were collected in clean containers

and labeled with necessary information for easy description of the samples. They

were then transported to the laboratory and refrigerated until tests were done.

Choice of sampling stations was based on the following rationale;

Areas with low and extreme pollution for purposes of comparison. The

assumption here was that the river was not highly polluted as it entered the

town, it got polluted in the town and thus its pollution load should have been

greater in the town.

Adequate spacing between the sampling stations for a more accurate study of

the pollution profile.

Areas with little or no settlements to avoid confrontations with hostile

residents.

To avoid polluted water at major outfalls such as drains, industrial outfalls,

stagnant pools and areas of standing water.

Cost effectiveness for collection, analysis and reporting.

3.4 CATCHMENT CHARACTERISTICS

The topography of the section of interest was determined by the softwares Google

Earth and Google maps. The figure shows a screen capture of the area from Google

Earth. The software gives altitudes and coordinates of points of interest. Software

with similar capabilities is Microsoft Encarta, but it is less powerful and accurate.

Using the software, the entire study area can be viewed. Attached are screen shots of

the entire study area as well as the individual sampling stations, complete with their

elevations and their coordinates, (Wikipedia).

Station 1: (Entry into Ruiru Town)

Altitude: 1901 meters

Flow characteristics: slow flowing

Color: clear

Odour: not detected

E25-0112/04 - 18 - OCHIENG S. (2010)

Main activities: farming, animal husbandry, clothes washing, (see plate 1), car

washing

Station 2: (Behind Henkel chemical industry)

Altitude: 1769 meters

Distance along the river from station A: 2.97 kilometers

Flow characteristics: mostly stagnant with very slow flow

Color: greenish grey with traces of light brown

Odour: noticeable trace of foul smell

Main activities: formal residential areas, river goes through farms and flows behind

industries, has effluent flowing from some pipes, (see plate 3).

Station 3: (Under Thika Road bridge)

Altitude: 1680 meters

Distance along the river from station B: 1.92 kilometers

Flow characteristics: slow moving, then very fast flowing after a waterfall near the

bridge.

Color: dark grey with traces of brown

Odour: noticeable trace of foul smell

Main activities: town life, business, industries, the river passes underneath Thika

road.

Station 4: (Exit Ruiru town)

Altitude: 1643 meters

Distance along the river from station C: 2.81 kilometers

Flow characteristics: slow flowing

Color: dark grey/ brown

Odour: foul, pungent smell

Main activities: Industrial processes, solid wastes (plastics, metals, papers dumped

along the river)

E25-0112/04 - 19 - OCHIENG S. (2010)

3.5 LABORATORY EXAMINATION OF WATER

The following Water Pollution Parameters were examined using standard methods,

(see appendix 4) (Andrew D. Eaton, LenorS.Clesceri, Arnold E. Greenberg, 1995).

1. Temperature

2. Chemical Oxygen Demand (COD)

3. Hydrogen ion concentration or pH

4. Dissolved Oxygen(DO)

5. Ammonia (DPD test)

E25-0112/04 - 20 - OCHIENG S. (2010)

CHAPTER 4

RESULTS AND DISCUSSION

The Ruiru Rivers‟ longitudinal profile shows that it stands at a mean altitude of

1901m at the town entrance and drops to 1680m at the Thika Road crossing after it

has gone through the town; a drop of 221m. The horizontal distance between the

entry point and the exit point is about 7.7 km. The slope of the river is fairly steep for

the upper section of the river. The slope is crucial in the creation of turbulent mixing

of regimes in the river, which enhances oxygen transfer (mixing) from the

atmosphere to the river. The data collected from the river is tabulated as shown in

table 1 below:

4.2 DATA COLLECTED/RESULTS

Date Sampling

station

Temperature

(oC)

Hydrogen ion

concentration

Mg/L

Dissolved

Oxygen

Mg/L

Chemical

Oxygen

Demand mg/L

Ammonia

Mg/L

4TH NOV 1

2

3

4

24

24

23

24

7.06

6.65

6.56

6.83

4.1

3.6

2.5

2.1

180

200

205

258

0.63

0.86

0.96

1.05

12TH NOV 1

2

3

4

22

23

23

22

8.57

8.36

8.23

7.53

3.8

3.4

3.2

2.6

208

225

238

249

0.76

0.92

1.15

1.25

19TH NOV

(wet day/

period)

1

2

3

4

22

22.5

22

23

8.73

8.33

7.85

7.56

4.4

4.1

3.6

3.3

155

185

188

203

0.55

0.59

0.67

0.78

19TH JAN 1

2

3

4

24

23

24

24

8.65

8.32

7.22

6.85

3.8

3.6

3.2

2.5

210

212

227

245

0.65

0.77

0.98

1.22

27TH JAN 1

2

3

4

24

23

24

23

8.63

8.26

7.96

7.65

3.6

3.5

2.8

2.3

198

255

268

305

0.83

0.96

1.23

1.26

9TH FEB 1

2

3

4

22.5

23

23

24

7.98

7.86

7.21

7.08

3.7

3.2

2.6

2.1

225

248

285

335

0.85

0.98

1.28

1.33

Around the midpoint of the river, human characteristics involve farming, car washing

and bathing. There is runoff from farms and domestic waste from the nearby Ruiru

municipal sewage treatment plant settling into the river. There is also significant

effluent coming from pipes behind the Henkel chemical industry just behind the river,

Table 1: collected data

E25-0112/04 - 21 - OCHIENG S. (2010)

located as shown on the Ruiru map. It is not clear exactly what kinds of effluent

discharge are deposited from the industries or where exactly the effluent discharge

pipes come from.

4.3 AVERAGES

Sampling

Station

Temperature

(x101) oC

Hydrogen ion

concentration

Mg/L

Dissolved

Oxygen

Mg/L

Chemical Oxygen

Demand

(mg/L)

(x102)

Ammonia

Mg/L

1 2.325 8.27 3.9 1.96 0.71

2 2.325 7.96 3.6 2.21 0.85

3 2.35 7.51 3.0 2.35 1.05

4 2.35 7.25 2.5 2.66 1.15

Table 2: Average values for the respective sampling stations

E25-0112/04 - 22 - OCHIENG S. (2010)

4.4 DATA ANALYSIS

4.4.1 Temperature

Fig 2: temperature variations for the four sampling stations

Temperature variations are mainly due to time of day when the samples were taken.

Dry periods registered higher values on average as compared to the wet period- 19th

Nov, (see fig 2). According to Kenyan standards, (see appendix table 3) the

temperature of water was within the required range of ambient temperature. There

was no indication of thermal pollution at any of the sampling stations. High

temperature in the river is responsible for killing aquatic life especially fish. It upsets

biological processes in the water that are responsible for breaking down organics.

21

21.5

22

22.5

23

23.5

24

24.5

4th Nov 12th Nov 19th Nov 19th Jan 27th Jan 9th Feb

Tem

pe

ratu

re 0

C

Sampling date

Temperature

Station 1

Station 2

Station 3

Station 4

E25-0112/04 - 23 - OCHIENG S. (2010)

4.4.2 Hydrogen ion concentration

Fig 3: hydrogen ion concentration (pH) for the four sampling stations

The pH is an important indicator of the status of the natural waters. The river pH

value can be used to indicate the health status of river. Most biological and chemical

reactions take place at normal pH range of between 6.5 and 8.5, (see appendix table

3), fig 3shows the pH profile of Ruiru River. These results indicated that the

discharges into the river did not affect the river pH, or that the river natural buffering

capacity was adequate to withstand any basic or acidic discharges. There is not much

variation in the pH values with the highest values being recorded at station 1 on four

different occasions. The recommended values lie within 6.5 and 8.5, and most of the

values recorded are within this range.

0

1

2

3

4

5

6

7

8

9

10

4th Nov 12th Nov 19th Nov 19th Jan 27th Jan 9th Feb

pH

Sampling date

Hydrogen ion concentration

Station 1

Station 2

Station 3

Station 4

E25-0112/04 - 24 - OCHIENG S. (2010)

4.4.3 Dissolved Oxygen

Fig 4: dissolved oxygen concentrations for the four sampling stations

The low DO concentration at station 4 downstream shows high microbial activity in

the river to the extent of depleting the dissolved oxygen. The wet period shows high

DO concentrations opposed to dry period, (see fig 4). The upstream areas are

characterized with higher DO concentration values. This profile shows how DO

concentration drops downstream showing higher presence of microbial activity

depleting oxygen. This shows evidence of organic pollutants and organic matter in

the river water downstream The DO upstream is relatively sufficient for aquatic life

as opposed to downstream. There is presence of solid waste and industrial effluent

downstream into the river. These wastes introduce a lot of suspended solids and

organics that reduce aeration of the river. The flow of the river upstream is fast due to

topography, this enables aeration that adds oxygen into the river. Downstream flows

are much slower limiting aeration. The DO values are below those of the Kenya

standards (see appendix table 3).

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

4th Nov 12th Nov 19th Nov 19th Jan 27th Jan 9th Feb

mg/

L

Sampling date

Dissolved oxygen

Station 1

Station 2

Station 3

Station 4

E25-0112/04 - 25 - OCHIENG S. (2010)

4.4.4 Chemical Oxygen Demand

Fig 5: chemical oxygen demand concentrations for the four sampling stations

The COD levels upstream at station 1 and station 2 change slightly, at this stage,

levels of COD are low and self-purification of the river is evident in reducing

organics in the river (see figure 5). This area is characterized by suburban residential

areas; discharge of pollutant into the river is fairly minimal. As the river enters the

town, it‟s seen that the COD level increase considerably. This is attributed to

discharge of waste from surrounding areas. At station 3 the COD level increase

sharply due to high loading by solid wastes, (see plate 3) which contains considerable

amount of organics. The data shows wet weather has a dilution effect on the COD

especially for downstream areas where dry weather COD levels is much higher than

wet weather COD levels. The high COD was evidence of presence of non-

biodegradable material substances in the river The Ruiru River is heavily polluted

with organics and chemical waste. The COD levels were way above the

recommended standards for natural river discharge (see appendix table 3).

0

50

100

150

200

250

300

350

400

4th Nov 12th Nov 19th Nov 19th Jan 27th Jan 9th Feb

mg/

L

Sampling date

Chemical Oxygen Demand

Station 1

Station 2

Station 3

Station 4

E25-0112/04 - 26 - OCHIENG S. (2010)

4.4.5 Ammonia

Fig 6: ammonia concentration variations for the four sampling stations

Ammonia concentration was lower at the upstream section of the river than at

downstream section (see figure 6).The ammonia concentrations are relatively low

indicating absence of human waste contamination at the sections tested. It increases

downstream up to station 4. The ammonia concentration for all stations is above the

recommended standards, (see appendix table 3), indicating pollution by chemicals

containing ammonia and fertilizes used in the farming area around Ruiru. The cause

of reduced levels of ammonia during wet period was due to dilution effect from

surface runoff.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

4th Nov 12th Nov 19th Nov 19th Jan 27th Jan 9th Feb

mg/

L

Sampling date

Ammonia

Station 1

Station 2

Station 3

Station 4

E25-0112/04 - 27 - OCHIENG S. (2010)

4.4.6 Averages

Fig 7: variations of the averages of the parameters tested with relation to the

sampling stations

The average values show station 1 having the highest average values for the hydrogen

ion concentration as well as the dissolved oxygen (see fig 7). The ph for station 1 lies

within the recommended values (see appendix table 3), the DO is however below the

recommended minimum value. The values reduce progressively as the river

progresses through and outside the town, evidence that the water gets polluted with

organics which use up the oxygen in the water, hence the reduction in the DO levels

(see fig 7). There are also chemical reactions that take place in the water hence the

progressive change in the pH values.

The Chemical Oxygen Demand (COD) and the ammonia levels increase gradually,

signifying high loading by solid wastes and other ammonia containing wastes. Both

the COD and ammonia levels are above those recommended by the various standards

even as at the time the river enters the town, (see appendix table 3) but they increase

to worse levels by the time the river exits the town.

23.1

23.15

23.2

23.25

23.3

23.35

23.4

23.45

23.5

23.55

0

1

2

3

4

5

6

7

8

9

Station 1 Station2 Station 3 Station 4

Tem

pe

ratu

re

mg/

L

Parameter

Averages

pH DO COD Ammonia Temperature

E25-0112/04 - 28 - OCHIENG S. (2010)

4.4.7 Pollution Profile

23.25 23.25 23.5 23.5

Elevation, Station 1, 1901

Elevation, Station 2, 1769

Elevation, Station 3, 1680 Elevation, Station 4, 1643

8.27 7.96 7.51 7.25

3.9 3.6 3

2.5 1.96 2.21 2.35 2.66

0.71 0.85 1.05 1.15

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

0

2

4

6

8

10

12

14

16

18

20

22

24

26

Station 1 Station 2 Station 3 Station 4

Ele

vati

n (

m)

valu

es

(mg/

L)

Sampling Stations

Temperature DO COD (x100) Ammonia pH Elevation

E25-0112/04 - 29 - OCHIENG S. (2010)

4.5 Discussion

From the River‟s flow profile on the previous page, the temperature is on a gradual

increase from 23.25 to 23.5 degrees Celsius. This temperature increase may be

attributed to a rise in metabolic reaction which can be as a result of the presence of

reactive effluent in the water. The effluent is chemically reactive thereby giving off

heat as a result of the metabolic processes that occur in the water body. The pH is on

a decrease from 8.27 to 7.25. The values are well within the recommended pH ranges

even though the reduction signifies a transformation from a more basic state to a

more neutral state, which is attained at pH of 7.0.

The values of the dissolved oxygen reduce from 3.9 mg/L to 2.5 mg/L which signifies

considerable consumption of the dissolved oxygen in the water as the river progresses

towards the exit of the town. The reduction is evidence of metabolic reactions in the

water which leads to the consumption of the dissolved oxygen and this may in turn

lead to the suffocation of the aquatic life present in the water. The values fall well

below the recommended value of 5.0 mg/L

The values of the Chemical Oxygen demand are on an increase from 196 mg/L to 266

mg/L. The high COD was evidence of presence of non-biodegradable material

substances in the river The Ruiru River is heavily polluted with organics and

chemical waste. The COD levels were way above the recommended standards for

natural river discharge which are recommended to be at not more than 50mg/L.

The values of ammonia are on a gradual increase from 0.71 mg/L to 1.15 mg/L.

Ammonia concentration was lower at the upstream section of the river than at

downstream section. The ammonia concentrations are relatively low indicating

absence of human waste contamination at the sections tested. It increases downstream

up to station 4. The ammonia concentration for all stations is above the recommended

standards; indicating pollution by chemicals containing ammonia and fertilizers used

in the farming area around Ruiru.

E25-0112/04 - 30 - OCHIENG S. (2010)

CHAPTER 5

CONCLUSIONS AND RECOMMENDATIONS

5.1 CONCLUSIONS

The pollution monitoring of the Ruiru River has revealed interesting results, and the

following conclusions have been arrived at after the analysis of the monitoring and

assessment of data obtained:

The field investigations coupled with laboratory analysis of samples obtained

from 4 monitoring stations from Ruiru River confirmed gross pollution of the

River. Most pollutants in the river exceed accepted discharge standards into

natural rivers.

The Ruiru River pollution increases as the river flows progressively

downwards. The upstream section shows lesser pollution, followed by the

middle section and the downstream section showing the highest pollution

load which is past the town.

The most polluted area was found to be downstream. This area is

characterized by solid waste and the water has a characteristic odour which is

strong and pungent. This is an indication of high microbial activity

(anaerobic) giving up a lot of gases. This also indicated presence of

chemicals with the pungent smell that has been introduced by industries in

the area. There is the need to create policies to mitigate pollution of riparian

bodies and ensure they are implemented.

E25-0112/04 - 31 - OCHIENG S. (2010)

5.2 RECOMMENDATIONS

To control pollution of River Ruiru, a lot has to be done. The following are some of

the measures that need to be taken to achieve this:

Clean up action plan be drawn up and to involve communities living and

operating along the Ruiru River. These are the informal settlements and the

industries.

The discharge of human waste into the river should be addressed through

efforts to have human settlements and agricultural activities within the river

relocated or stopped.

The industrial discharges should be stopped through efforts by the industries

to take measures to address pollution emanating from their production

processes. In the industrial and commercial areas, there is need to install

automatic water quality detectors to ensure no illegal industrial effluents are

discharged into the rivers at night. Impromptu water samples should also be

taken at night for analysis to ascertain the quality status of the river water

regularly.

Some technical and financial support should be considered in developing

technologies to pre-treat discharges from industries within their premises.

There is need, to look at the existing legislation in relation to environmental

pollution, penalties and enforcement.

Continue to build the capacity of the Local Authorities through improvement

of the monitoring laboratories and equipment as well as organizing refresher

courses.

Continuous monitoring of the river to ascertain that the pollution levels are

within recommended levels.

Studies on polluter‟s pay principle should be initiated with a view to assess

the capacity of the existing treatment plants and sewer system to handle more

concentrated waste discharges.

E25-0112/04 - 32 - OCHIENG S. (2010)

Engineering solutions to clean up efforts should be investigated such as

channeling, introduction of flow weirs in the river in order to increase the

flow conditions, especially on the stagnant sections of the river to enhance

the river self-purification and increase oxygen dissolution.

Initiate efforts of assessment of pollution, community sensitization and clean

up action plan The Ruiru River.

There is need to create a buffer zone between the river banks and human land

use activities to avoid any tendency of dumping any wastes into the rivers.

The informal activities (Jua-Kali Motor garages) and Food Kiosks which dot

most of the river sub-basin profiles should be sited far away from the river

banks. These discharge and dump waste oils and solid garbage onto the rivers

and hence pollute the waters.

A vigorous campaign to educate people on the importance of a clean

environment and the danger of polluted waters should be initiated

immediately. The focus should be a zero tolerance of garbage and solid

wastes and limited generation of the same at the household level. The town

council of Ruiru needs to consider a viable use of the river waters which can

sensitize the town‟s inhabitants on the need to take care of the waters. This is

one factor which has necessitated the clean-up campaigns of river waters in

the developed countries where some of the rivers passing through major cities

have since been cleaned and are now habitable for many uses.

There should be initiated a proper Solid waste collection and disposal

mechanism. A community approach should be adopted in solid waste

handling. Separation of solid waste before disposal would go a long way in

solving collection problems especially by recycling industries which need to

be encouraged to collect the waste from generation points. Since recycling is

the ultimate solution to control solid waste, every effort to make it more

efficient must be explored, this being one of them. Community approach

would reduce institutional spending and promote more responsible garbage

and in the long run a more responsible and environmentally sensitive society.

E25-0112/04 - 33 - OCHIENG S. (2010)

BIBLIOGRAPHY/REFERENCES

Andrew D. Eaton, Lenor S. Clesceri, Arnold E. Greenberg, (1995).Standard methods

for the examination of water and waste water. American Health association,

19th edition.

David Kuria, Ecotact, (2004) Best practices for environmental conservation for River

Basin programs.

Kenya Standards Legislation, 2006. Second schedule; Water quality monitoring

sources of domestic water.

Third Schedule; Standards for Effluent discharge into the environment.

K.V. Ellis, (1989).Surface water Pollution and its control. Macmillan Press Ltd 1989.

Microsoft® Encarta® 2005© encyclopedia.

Ministry of land reclamation, regional and water development discharge standards.

SEPA: Diffuse Pollution reports, http://www.sepa.org.uk/dpi/whatis/index.htm

(Last accessed 13th November 2009)

UNEP: Environmental Management Information System (EMIS),

http://www.unep.org/roa/Nairobi_River_Basin/default (Last accessed 13th

November 2009).

Wandiga, S. O (1996.) River Pollution In Developing Countries-A case study III:

Effect of Industrial Discharges on Quality of Nairobi River Waters in Kenya

Wikipedia: http://www.wikipedia.org/wiki/River (Last accessed 13th November 2009)

Wikipedia: Biosafety News, October/November 2002: Nairobi river pollution a threat

to health, http://www.wikipedia.org/wiki/Nairobi_River (Last accessed 13th

November2009)

World Health Organization's drinking water standards 1993: Guidelines for Drinking

Water Quality.

Geneva. The international reference point for standard-setting and drinking-water

safety.

World Health Organization/European Union drinking water standards comparative

table: The EU standards (1998)

E25-0112/04 - 34 - OCHIENG S. (2010)

APPENDIX

APPENDIX 1: BUDGET

EXPENDITURE COST(Kshs)

Chemical Oxygen Demand (C.O.D) test 4,000

Ammonia test 2,000

Dissolved Oxygen (DO) test 2,000

Printing, binding and miscellaneous. 2,000

Data collection and transport 1,000

TOTAL 11,000

Table 6: budget for the whole project

APPENDIX 2: SCHEDULE

1st SEMESTER 2

nd SEMESTER

WEEK NO. 2 3 4 6 7 8 9 10 4 5 6 7 8 10 11 12

Topic

Proposal

Data

Collection

Presentation

Literature

review

Visit to the

study area

Laboratory

Tests

Progress

report

Final report

compilation

Report

submission

Table 7: schedule for the project duration

E25-0112/04 - 35 - OCHIENG S. (2010)

APPENDIX 3: TABLES OF STANDARDS

APPENDIX 3.1: Kenya standards

Parameter Guide value

(maximum

allowable limit)

Station 1 Station 2 Station 3 Station 4

pH 6.5 – 8.5 8.27 7.96 7.51 7.25

Ammonia 0.5 (mg/L) 0.71(mg/L) 0.85(mg/L) 1.05(mg/L) 1.15(mg/L)

DO 5.0 mg/L 3.9(mg/L) 3.6 (mg/L) 3.0(mg/L) 2.5(mg/L)

COD 50 (mg/L) 196(mg/L) 221(mg/L) 235(mg/L) 266(mg/L)

Table 3: Kenya standards for water

APPENDIX 3.2: World Health Organization Standards

Parameter Guide value

(maximum allowable

limit)

Station 1 Station 2 Station 3 Station 4

pH 6.5 - 8.5 8.27 7.96 7.51 7.25

Ammonia 0.2 mg/l (up to 0.3

mg/l in anaerobic

waters)

0.71(mg/L) 0.85(mg/L) 1.05(mg/L) 1.15(mg/L)

DO 5.0 mg/L

about 75%

saturation

3.9(mg/L) 3.6(mg/L) 3.0(mg/L) 2.5(mg/L)

COD 50(mg/L) 196(mg/L) 221(mg/L) 235(mg/L) 266(mg/L)

Table 4: World Health Organization standards for water

APPENDIX 3.3: European Standards

Parameter Guide value

(maximum allowable

limit)

Station 1 Station 2 Station 3 Station 4

pH 6.5 – 8.5 8.27 7.96 7.51 7.25

Ammonia 0.5 mg/L

0.71(mg/L) 0.85(mg/L) 1.05(mg/L) 1.15(mg/L)

DO at least 5.0 mg/L 3.9 (mg/L) 3.6(mg/L) 3.0(mg/L) 2.5(mg/L)

COD 50 (mg/L) 196 (mg/L) 221(mg/L) 235(mg/L) 266(mg/L)

Table 5: European standards for water

E25-0112/04 - 36 - OCHIENG S. (2010)

APPENDIX 4: PROCEDURES

4.1 Temperature

The temperature was determined on-site at the time of sampling. This was done by

simply inserting a thermometer into the sampling point within the river and taking a

reading. Precaution was however taken to ensure the thermometer was not damaged,

therefore very turbulent areas of the river should were avoided, thereby making sure

the possibility of having debris that may break the bulb of the thermometer was

minimized.

4.2 COD (Open Reflux Method)

Introduction: it is used as a measure of the oxygen equivalent of the organic matter

content of a sample that is susceptible to oxidation by strong chemical oxidant. The

test is usually carried out for monitoring and control of wastewater processes.

Reagents:

Distilled water

Standard potassium dichromate solution, 0.025N

Sulphuric acid concentrated reagent containing silver sulphate

Standard ferrous ammonium sulphate, 0.025N

Powdered mercuric sulphate

Phenanthroline ferrous sulphate (indicator)

Apparatus:

Reflux apparatus with ground glass joint

250ml Erlenmeyer flask with ground glass joints

Pipettes

E25-0112/04 - 37 - OCHIENG S. (2010)

Procedure:

1. 50ml of the sample was placed in 500ml refluxing flask.

2. 1gm of mercuric sulphate, several glass beads were added into the solution. 5ml

of H2SO4 (concentrated sulphuric acid) was added slowly while mixing to

dissolve the mercuric acid.

3. The sample was mixed while cooling to avoid possible losses of volatile

materials.

4. 25ml of 0.0471M K2Cr2O7 solution was added and mixed thoroughly.

5. The samples were then transferred to the Liebig condenser apparatus. The

remaining sulphuric acid reagent (70ml) was then added through the open end

of the condenser.

6. The samples were continuously stirred while adding the acid reagent.

7. The reflux mixture was mixed thoroughly by applying heat to prevent local

heating of the flask bottom and a possible blow out of the flask contents.

8. The open end of the condenser was covered with a foil to prevent foreign

materials from entering the refluxing mixture.

9. Refluxing was then carried out for 2hours.

10. The condenser was thereafter cooled and washed down using distilled water.

11. The reflux was then disconnected and diluted to about twice its original volume

with distilled water.

12. This mixture was then cooled to room temperature (due to the exothermic

nature of the reaction). The excess k2cr2o7 was then titrated using FAS using

0.1-0.15ml (2 to 3 drops) ferroin indicator.

13. The same volume of ferroin indicator was used for all titrations.

14. The end point of the reaction was taken as the first sharp change in colour, from

blue-green to reddish brown.

15. Similarly a blank of equal volume to sample, distilled water was titrated against

FAS.

Calculations:

COD = (A-B) x m x 8000)

ml of sample

Where: A = ml, FAS used for blank water

B = ml, FAS used for sample water

m = molarity of the FAS

E25-0112/04 - 38 - OCHIENG S. (2010)

4.3 Dissolved Oxygen (DO), Titration Method

Introduction:

It is required for supporting fish and aquatic life in water. When it reaches the level

below 2mg/l some aquatic life die.

Reagents:

1. Manganous sulphate solution. Mnso4.7h20.

2. Alkaline azide iodide solution.

3. Sulphuric acid solution.

4. Starch indicator.

5. Standard sodium thio-sulphate solution, 0.025N

Procedure

1. 200ml of the sample was collected in a beaker.

2. 1ml of manganous sulphate was added to the sample while stirring. A pipette

was used during the experiment.

3. 1ml of alkaline azide iodide was then added to the sample whilst stirring.

Some precipitates formed.

4. 1ml of concentrated sulphuric acid was then added to the mixture. The

sulphuric acid dissolved the precipitates.

5. 5 drops of starch indicator were added to the mixture. At that point the

mixture turned blue-black colour.

6. The mixture was then titrated against standard sodium thio-sulphate solution.

Calculations:

The 200ml of solution taken for titration corresponds to 200ml of the original sample,

because 1ml of 0.025N sodium thio-sulphate solution titrant is equivalent to 0.2mg

DO, each milliliter of sodium thio-sulphate titrant is equivalent to 1mg/lt DO. When

volume equal to 200ml of the original sample is titrated, therefore the DO

concentration is ml of titrant used under the above conditions.

E25-0112/04 - 39 - OCHIENG S. (2010)

4.4 Hydrogen Ion Concentration or pH (Using The pH Meter Method.)

Procedure

1. Approximately 75ml of sample was placed in a 100ml beaker.

2. The electrodes were carefully raised out of the beaker and rinsed with

distilled water. Drops of water were wiped from the electrodes.

3. The electrodes were immersed in a beaker containing a blank sample and

used to calibrate the pH Meter.

4. The electrodes were immersed in the beaker containing the sample.

5. The pH was read directly from the indicator screen on the pH meter.

6. The electrodes were carefully raised, rinsed with distilled water and replaced

in a beaker of distilled water.

4.5 Ammonia Test (DPD Method)

The range is between 0 to 1.0 mg/1N. For higher concentrations dilute the sample and

multiply result with a factor

Apparatus

a) Photometer at 640nm

b) Round test tube 10ml

Reagents

1. Palintest Ammonia No 1 tablets

2. Palintest Ammonia No 2 tablets

Procedure

2. The test tube was filled with the sample to the 10ml mark

3. One ammonia No 1 and one Ammonia No.2 tablet were added, crushed and

mixed to dissolve

4. The solution was then let for ten minutes to allow colour development

5. A wavelength of 640nm was selected on the photometer

6. The photometer reading (% T) was then taken in the usual manner.

The ammonia calibration chart was then consulted to find the Ammonia concentration

in the sample.

E25-0112/04 - 40 - OCHIENG S. (2010)

APPENDIX 5 : PLATES

Plate 5: Google earth image of the

section showing the river crossing

under Thika road

Plate 4: the water fall section

near Thika road

Plate 7: the researcher taking samples at sampling

station 2, wet period, note the rise in water level,

compare to plate 7

Plate 6: sampling point for

station; dry period.

E25-0112/04 - 41 - OCHIENG S. (2010)

Plate 8: stagnant and polluted section

of the river

Plate 11: the researcher testing samples in the University

laboratory

Plate 9: the researcher collecting

samples from station 3

Plate 10: car washing in the river;

one of the sources of pollution in

the river