UNIVERSITY OF NAIROBI PROJECT

UNIVERSITY OF NAIROBI

A STUDY OF PIPED WATER QUALITY COMPLIANCE

AROUND THE UNIVERSITY OF NAIROBI.

By

WANJIRU WILFRED GATIMU

F16/40376/2011

A project submitted as a partial fulfilment for the requirement for the

award of the degree of

BACHELOR OF SCIENCE IN CIVIL ENGINEERING

Year of submission

(2016)

i

Abstract

The objective of the surveillance was to collect and collate information that helps in promoting

improvement of water supply vis--vis quality. The water quality was in compliance with the

Kenya standards which are based on health criteria given by WHO water quality guidelines. The

study was accomplished by establishing sampling points around the University of Nairobi that are

strategically defined by the NCWSC.

Water quality was assessed by conducting experiments and analysing the data. The water samples

were tested for typical parameters namely; chemical substances, physical properties and

bacteriological quality. Laboratory testing was carried out at the UON Public Health Laboratory

and the Kabete Water Treatment laboratory. Thereafter, the parameters were compared with water

quality guidelines given by WHO, KEBS and WASREB. All the parameters were within the

recommended except the free residual chlorine in Central Park which was 0.1mg/l, a value below

the recommended minimum of 0.2mg/l.

The water supplied quality parameters were found to be in compliance, therefore clean and safe

for consumers. This report is based on data collected for the month of February 2016.Evidently,

water quality management is a complex activity and requires the accomplishment of compliance

to water quality standards (Chapman 1996). Therefore, clear and appropriate measures for water

quality management should be put in place.

ii

Dedication

I would like to dedicate this report to my dearest sister, to my best friend and my guardians for

their unwavering support and motivation throughout my study.

iii

Acknowledgement

First and foremost, I would like to thank the Almighty God for this far He has brought me and the

gift of able parents who are always there to guide and show moral support through my education.

Special gratitude and appreciation to all those gave me the possibility to successfully complete this

project. I thank my final year project supervisor, Eng. D.M. Wanjau, whose help, stimulating

suggestions, encouragement and the help to coordinate my project especially in writing this report.

For all the staff, both from UON and NCWCS, I acknowledge with much appreciation their crucial

role especially in the laboratories and the permission to use the required equipment and necessary

chemicals to complete the report.

iv

Table of Contents

Abstract ............................................................................................................................................ i

Dedication ....................................................................................................................................... ii

Acknowledgement ......................................................................................................................... iii

Illustrations .................................................................................................................................... vi

Abbreviations ............................................................................................................................... viii

Chapter One .................................................................................................................................... 1

Introduction ..................................................................................................................................... 1

1.1 General ............................................................................................................................. 1

1.2 Problem statement ............................................................................................................ 2

1.3 Objectives ......................................................................................................................... 2

Chapter Two.................................................................................................................................... 3

Literature Review............................................................................................................................ 3

2.1 Overview of existing water supply in Nairobi ................................................................... 3

2.2 Introduction ....................................................................................................................... 6

2.3 Aesthetic Parameters of Water ......................................................................................... 9

2.4 Microbiology and Bacteriological Aspects..................................................................... 12

2.5 Chemical Parameters ...................................................................................................... 13

2.6 Surveillance and Monitoring .......................................................................................... 18

2.7 Sampling ......................................................................................................................... 21

2.8 Health implications ......................................................................................................... 23

2.9 Treatment and disinfection ............................................................................................. 30

2.9.1 Water treatment process ............................................................................................. 30

2.9.2 Chlorination ................................................................................................................ 32

Chapter Three................................................................................................................................ 33

Methodology ................................................................................................................................. 33

3.1 Introduction ........................................................................................................................ 33

3.2 Study area........................................................................................................................... 33

3.3 Limitations of the study ..................................................................................................... 35

3.4 Sampling ............................................................................................................................ 35

3.5 Laboratory tests .................................................................................................................. 36

3.6 Questionnaire ..................................................................................................................... 37

v

Chapter Four ................................................................................................................................. 38

Results and Analysis ..................................................................................................................... 38

Chapter Five .................................................................................................................................. 49

Discussions ................................................................................................................................... 49

5.1 Physiochemical aspects ...................................................................................................... 49

5.2 Acceptability aspects ......................................................................................................... 50

5.3 Bacteriological quality ....................................................................................................... 51

5.4 Other parameters considered.............................................................................................. 51

Chapter Six.................................................................................................................................... 52

Conclusions ................................................................................................................................... 52

Chapter Seven ............................................................................................................................... 54

Recommendations ......................................................................................................................... 54

References ..................................................................................................................................... 55

Appendices .................................................................................................................................... 57

Appendix I: Schedules .................................................................................................................. 57

Appendix II: Tables ...................................................................................................................... 60

Appendix III: Pictorials................................................................................................................. 61

vi

Illustrations

List of Charts

Chart 1:Turbidity analysis of results. ............................................................................................ 40

Chart 2: pH analysis of results. ..................................................................................................... 41

Chart 3: Colour result analysis. ..................................................................................................... 42

Chart 4: Residual chlorine results analysis. .................................................................................. 43

Chart 5: Conductivity result analysis. ........................................................................................... 44

Chart 6: Analysis of fluorides results............................................................................................ 45

Chart 7: Analysis of hardness results. ........................................................................................... 46

Chart 8: Analysis of results for total alkalinity. ............................................................................ 47

Chart 9: Analysis of results for TDS............................................................................................. 48

List of Figures

Figure 1:Schematic layout of water sources, treatment and transmission system (BRL and

Suereca, 2010)................................................................................................................................. 4

Figure 2:General layout of Distribution Network (Saureca, 2007) ................................................ 5

Figure 3:Sampling points around the University environs. .......................................................... 34

Figure 4:Sampling points in Nairobi County ................................................................................ 34

List of Tables

Table 1: Hardness ......................................................................................................................... 15

Table 2: Minimum sample numbers for piped drinking-water in the distribution system. .......... 22

Table 3: WHO drinking water guidelines ..................................................................................... 25

Table 4: Microbiological limits for drinking water and containerized water. .............................. 26

Table 5: Aesthetic Quality for Requirements of Drinking water and Containerized water (KS 150

and WHO Guidelines)................................................................................................................... 27

Table 6: Aesthetic quality requirements for drinking water and bottled drinking water (adopted

from KS 05-459: Part 1:1996). ..................................................................................................... 28

Table 7: Microbiological limits for drinking water and containerized drinking water (Adopted

from KS 05-459: Part 1:1996). ..................................................................................................... 29

Table 8: Ranking of technical complexity and cost of water treatment processes. ...................... 31

Table 9: Recommended treatment in relation to number of coliform organism per 100ml. ........ 31

vii

List of Pictorials

Photograph 1: Mixing of the sample with DPD tablet (Serena Hotel) ......................................... 61

Photograph 2:Reading the concentration of Residual Chlorine .................................................... 61

Photograph 3:Testing of pH .......................................................................................................... 62

Photograph 4: Testing conductivity of the samples ...................................................................... 62

Photograph 5:Alkalinity test through titration .............................................................................. 63

Photograph 6:Turbidimeter at Kabete Treatment Works.............................................................. 63

Schedule 1: WSP Sample Schedules for Water Quality Monitoring ............................................ 20

viii

Abbreviations

Acronym Meaning

CaCO3 Calcium Carbonate

F.T.U. Formazin Turbidity Units

KEBS Kenya Bureau of Standards

Mg/l Milligrams per litre

M.P.N. Most Probable Number

NCWSC Nairobi City Water and Sewerage Company

NaCl Sodium Chloride

N.T.U. Nephelometric Turbidity Units

pH Concentration of hydrogen ion

P.H.E. Public Health Education

Ppm parts per million

T.C.U. True Colour Units

TDS Total Dissolved Solids

U.O.N. University of Nairobi

S Micro Siemens

W.H.O. World Health Organization

WASREB Water Services Regulatory Board

WSB Water Service Board

WSP Water Service Provider

1

Chapter One

Introduction

1.1 General

Over the years, especially in developing countries, consumers have encountered substandard water

supply. This has been a significant danger to the health and well-being of the consumer. The water

supply agencies have a responsibility to serve the community with quality water as specified in

the World Health Organization (WHO) standards. Here in Kenya, WASREB has stipulated local

standards mostly from the WHO water quality guidelines.

However, due to the vulnerability of water to contamination there is need for continuous and

frequent assessment of its quality before supply to the community. Hence, the surveillance of the

water quality standards can be done either on site at various supply points or the parameters tested

in a laboratory. The latter is then checked if it complies with the requirements stipulated in the

standards.

Water suppliers need to carry out a wider range of analyses relevant to the operation and

maintenance of water-treatment and distribution systems, in addition to the health-related

parameters laid down in national water-quality standards.

Evidently, all people whatever the stage of development, social and economic backgrounds have

the right to access adequate supply of safe drinking water. Cost effective improvement of drinking

water quality at tap involves source water quality improvement, better water management and

advances in water treatment technology.

2

1.2 Problem statement

The Nairobi water utility NCWSC has the stringent water quality monitoring programs to ensure

the water they supply the city is safe for drinking and domestic purposes. However, due to high

leakage and pipe bursts in the network and intermittent supply, water is sometimes contaminated

before it reaches the tap. These kind of leakages sometimes occur along areas with sewage

overflows. Therefore, for those who cannot afford bottled water or boil the water, they have to

take chances with tap water.

Most people residing within and around the University of Nairobi rely on piped water for

consumption. Although its the most reliable means; if not monitored the health of the consumers

is at risk. This poses danger, of the water supplied to communities not being well monitored, to

curb the hazards caused by substandard water. Often, the source of water dictates the treatment

requirements before supply. However, even after treatment there is need to monitor the quality of

the water at various supply points. This continuous assessments ensure that the consumer gets safe

water.

Water obtained from boreholes as underground water should be monitored to ensure it meets the

standards cut. More often than not, borehole water is not treated.

As part of the quality assurance program and process control, WSPs are required to undertake their

own monitoring of water quality. Drinking-water suppliers are responsible at all times for the

quality and safety of the water that they produce (WHO, 2011).

1.3 Objectives

1. To determine if the quality of the water supplied to the university environs meets the minimum

requirement of WHO, KEBS, and WASREB guidelines.

2. It seeks to ensure a minimum required number of samples and tests on water supply and

collected data is compliant to the standards.

3. To evaluate the safety of the water consumed by the public residing around the water supply

region.

4. To bring out the challenges faced in water quality monitoring.

3

Chapter Two

Literature Review

2.1 Overview of existing water supply in Nairobi

The water supply of Nairobi city is made up of the sources, treatment and storage, and distribution

systems. Among the sources Sasumua, Ruiru and Thika (Ndakaini) dams and Kikuyu springs. The

existence of private boreholes and other local water sources such as streams or rivers and spring

well also contribute considerably to supply.

Sasumua dam is located about 90km north of Nairobi city. It was constructed on the Sasumua

stream, a tributary of the Chania River on the south end of Aberdare Ranges. It has a water

treatment plant with a daily capacity of 63,700m3 (BRL and Seureca, 2010).

Thika dam also located about 80km north of Nairobi city. Its water is transported to Ngethu

Treatment Works through a series of tunnels and pipelines. Ngethu treatment plant has a daily

capacity of 457,900m3 (BRL and Seureca, 2010).

Ruiru dam is located about 40km north of Nairobi city. Its raw water is transported to Kabete

Water Treatment Works through pipelines. The design capacity of the transmission lines is

30,000m3 every day (BRL and Seureca, 2010).

Kikuyu springs is a small source compared to the rest. It is located about 19km west of Nairobi

city. Supply from kikuyu spring is estimated about 4,800m3 every day (BRL and Seureca, 2010).

4

Figure 1:Schematic layout of water sources, treatment and transmission system (BRL and

Suereca, 2010)

5

Water distribution system.

The water distribution network is about 480km2. The city is conveniently divided into 11

distribution pressure zones (BRL and Seureca, 2010). The distribution system integrates both

storage tanks and booster station strategically sited in terms of demand and the hydraulic operation

requirements.

Figure 2:General layout of Distribution Network (Saureca, 2007)

6

2.2 Introduction

To sustain life, water is essential and should be adequate, safe and accessible. For human health,

the quality of drinking water provides significant benefits to avoid diseases related contamination.

As stated by WHO (2008), safe drinking water does not represent any significant risk to health

over a lifetime of consumption, including different sensitivities that may occur between life stages.

A guideline value represents the concentration of a constituent that does not result in any

significant risk to the health of the consumer over a lifetime of consumption. Whenever a guideline

value is exceeded, this should be a signal to investigate the cause with a view to taking remedial

action or to consult with the authority responsible for public health. Although the guideline values

describe a quality of water that is acceptable for life long consumption, the establishment of these

guideline value should not be regarded as implying that the quality of drinking water maybe

degraded to the recommended level. Indeed, a continuous effort should be made to maintain

drinking water quality at the highest possible level (WHO, 1997).

In case of short-term deviations to the guideline value, it is does not necessarily mean that the

water is unsuitable for consumption. The amount by which, and the period for which, any guideline

value may be exceeded without affecting public health depends upon the specific substance

involved. It is recommended that in such a case, the surveillance agency should be consulted for

suitable action, taking into account the intake of the substances from sources other than drinking

water, the toxicity of the substance, the likelihood and nature of any adverse effects and the

practicability of the remedial measures.

Guidelines that were considered for the report are:

i. WHO guidelines which are international standards for drinking water (Table 3).

ii. KEBS guidelines which are Kenyan national standards for drinking and containerized

water borrowed from WHO (Table 4&5 ).

iii. WASREB guidelines that are borrowed from the Kenya Standards by the Water Service

Requlatory Board to ensure Water Service Providers meet the cut (Table 6&7).

7

2.2.1 Quality standards

Standards provide a common reference point for the assessment of the quality of goods and

services (KEBS). They ensure that products and services are safe, reliable and of preferred quality.

2.2.2 Water quality

Water quality is one of the main indicators of the quality of service provided to the consumer,

therefore has an impact on both the public health and aesthetic value of the water. It can be thought

of as a measure of the sustainability of water for a particular use based on selected physical,

chemical and biological characteristics. A drinking-water quality guideline value represents the

concentration of a constituent that does not result in any significant health risk to the consumer

over a lifetime of consumption. Drinking-water should be suitable for human consumption and for

all usual domestic purposes. Regulatory government agencies must always maintain surveillance

on water supplied to the public. When a guideline value is exceeded, the cause should be

investigated and corrective action taken.

Although guidelines for drinking-water quality are based on the best available public health advice,

there is no guarantee that consumers will be satisfied or dissatisfied by water supplies that meet or

fail to meet those guidelines (WHO, 1997). It is therefore wise to be aware of consumer perceptions

and to take into account both health-related guidelines and aesthetic criteria when assessing

drinking-water supplies. In drawing up national standards for drinking-water quality, it will be

necessary to take into account various local, geographical, socioeconomic and cultural factors. As

a result, national standards may differ appreciably from the guideline values.

Water quality Assessment: is the overall process of evaluation of the physical, chemical and

biological nature of water in relation to natural quality, human effects and intended uses,

particularly uses which may affect human health and the health of the aquatic system itself

(Chapman, 1996).

8

Water quality Monitoring: is the actual collection of information at set locations and at regular

intervals in order to provide the data which may be used to define current conditions, establish

trends, etc. It is long-term, standardized measurement and observation of the aquatic environment

in order to be used for interpretation and assessment (WHO, 1997).

I. Surface water quality (WASREB)

The natural and human activities that cause change of quality of surface water include;

Weathering rocks and erosion.

Decay of organic matter such as leaves, branches of trees which result in humid substances.

Flooding river banks resulting in high turbidity.

Industrial and domestic wastes such as oil and grease, detergents, inorganic salts etc.

Agricultural runoff including fertilizers, herbicides and pesticides.

II. Ground water quality (WASREB)

Ground water obtained from boreholes contains no or low levels of harmful pathogens but it can

be polluted with naturally occurring chemicals. More often than not, contamination can be caused

by poor sanitary protection at the top of the borehole. Composition of ground water highly depends

on;

Composition of the soil (humic substances, organic matter and minerals).

Retention time of ground water.

Quality of water to be infiltrated for example rain or surface water.

9

2.3 Aesthetic Parameters of Water

2.3.1 Turbidity

Turbidity is a measure of the amount of light dispersed by the particles suspended in a sample of

water. It is a function of the concentration and the nature of the particles. It is caused by presence

of suspended matter such as clay, silt and fine particles of organic and inorganic matter, plankton

and other microscopic organisms. Turbidity is usually measured using a turbidimeter which works

on the principle of light scattering. The amount of light scattered is proportional to the turbidity of

the liquid and can be measured. The WHO guideline value for turbidity is 5NTU or FTU and above

this value, water can be objected to aesthetic reasons while a value of less than 1NTU or FTU is

preferred for disinfection efficiency. Presence of clay and other inner suspended particles in

drinking water may not adversely affect the health but may cause need for additional treatment.

Soon after rainfall, variation in ground water turbidity may be an indication of surface

contamination. A turbidity indicating surface runoff suggest possible pollution therefore requires

satisfactory treatment before supply to the public (PHE lecture notes 481, 2014).

Turbidity affects the acceptability of water to the consumers and the selection as well as the

efficiency of the treatment process to be conducted. Whenever the treatment involves disinfection

with chlorine, turbidity exerts a chlorine demand and protects microorganisms and may also

stimulate the growth of bacteria (WHO, 2008).

2.3.2 Colour

Colour in drinking water may be due to the presence of organic matter such as humic substances,

metals such as iron and manganese, or highly coloured industrial wastes (WHO, 2008). It is an

indication of large amount of organic chemicals in adequate treatment and high disinfection

demand. The colour in unpolluted surface waters is caused by the presence of humic and fulvic

acids which are derived from peat and soil humus. In some waters the brown colour is enhanced

by the presence of iron and manganese. Waters subject to industrial pollution may also contain a

wide variety of coloured materials.

10

The colouring materials may be procured by surface water when flowing through swamps or by

groundwater when dissolving minerals. Red water results from the presence of iron compounds in

water. Swampy water appears black due to ink formed by the combination of organic acids with

tannates and gallates. Blue water may result from copper compounds in suspension or in solution

or from landing bluing (Leonard, 1973)

2.3.3 Odour

Odour is an unpleasant distinctive smell that is caused by the presence of organic substances in

water (WHO, 2008). Some odours are indicative of increased biological activity, while others may

originate from industrial or municipal discharges in to natural sources therefore causing algae

growth.

The odour of water changes with temperature and sometimes not being noticeable when water is

cold. Water for domestic use should have no odour. The intensity of odour is expressed as threshold

odour, based on diluting a portion of sample of water with odour free water. While in the fields of

stream pollution and air pollution, the threshold odour test expresses odour in parts per million

(ppm).Sanitary surveys should include investigations of sources of odour when problems are

identified.

2.3.4 Taste

Taste is the combined perception of substances detected by the senses of taste and smell. Taste

problems in drinking water supplies are often the largest single cause of consumer complaints.

Changes in the normal taste of a public water supply may signal changes in the quality of the raw

water sources or deficiencies in the treatment process (WHO, 2008).

It may originate from the treatment process as a result of chlorination or through water reacting

with substances in the water distribution pipes such as asphaltic or bituminous coating on pipes or

reservoirs.

Some substances such as certain organic salt produce a taste without an odour and can be evaluated

by a taste test. Furthermore, other sensations ascribed to the sense of taste are odour, even though

the sensation is not noticed until the substance is consumed.

Water should be free of tastes that would be objectionable to the majority of consumers.

11

2.3.5 Temperature

Cool water is generally more palatable than warm water, and temperature will have an impact on

the acceptability of a number of other inorganic constituents and chemical contaminants that may

affect taste. High water temperature enhances the growth of microorganisms and may increase

problems related to taste, odour, colour and corrosion (WHO, 2011).

2.3.6 Total dissolved solids

Total dissolved solids are a measure of all inorganic and organic substances contained in a liquid

in molecular, ionized or micro-granular suspended form. Total dissolved solids are normally

discussed in fresh water systems as salinity comprises of some of the ion constituting the definition

of TDS. The principal application of TDS is in the study of water quality for streams, rivers and

lakes and although TDS is not considered a primary pollutant, it is used as an indicator of aesthetic

characteristics of drinking water and as an aggregate indicator of the presence of a broad array of

chemical contaminants. (Total dissolved solids-Wikipedia the free encyclopaedia). The amount of

TDS contained in water vary considerably with the different geologic conditions due to the

differences in the solubility of minerals.

2.3.7 Conductivity

Electrical conductivity is the ability of a substance to conduct an electrical current, measured in

Micro Siemens per centimetre. The higher the conductivity the greater the number of ion in the

water. Ions such as sodium, potassium, and chloride give water higher conductivity. Conductivity

can be an indicator of the amount of dissolved salts in a sample. Conductivity often is used to

estimate the amount of total dissolved solids (TDS) rather than measuring each dissolved

constituent separately (Farrell-Poe, 2005)

12

2.4 Microbiology and Bacteriological Aspects

Microbial parameters have an immediate and significant impact on human health and have to be

analysed frequently (WHO, 2008). Microorganisms are usually very small living organisms which

can only be seen with the help of a microscope. Many species of the organisms have been identified

and studied extensively. Engineers are interested in microorganisms that are involved in causing

water-borne diseases, decomposition and stabilization of organic matter and useful reactions that

are gainful e.g.: industrial production of alcoholic beverages, fermented dairy products, vitamins,

enzymes etc.

Particularly, public health engineers have interest on how pathogens find their way into water,

their movement from one point to another and their behaviour in relation to change of environment

in a water supply system.

2.4.1 Escherichia coli (E. coli)

Is abundant in human and animal faeces; in fresh faeces it may attain concentrations of 109 per

gram. It is found in sewage, treated effluents, and all natural waters and soils subject to recent

faecal contamination, whether from humans, wild animals, or agricultural activity. Recently, it has

been suggested that E. coli may be present or even multiply in tropical waters not subject to human

faecal pollution. However, even in the remotest regions, faecal contamination by wild animals,

including birds, can never be excluded. Because animals can transmit pathogens that are infective

in humans, the presence of E. coli or thermotolerant coliform bacteria must not be ignored, because

the presumption remains that the water has been faecally contaminated and that treatment has been

ineffective (WHO, 2008).

2.4.2 Coliform organisms (total coliforms)

Coliform organisms have long been recognized as a suitable microbial indicator of drinking-water

quality, largely because they are easy to detect and enumerate in water. The term coliform

organisms refers to Gram-negative, rod-shaped bacteria capable of growth in the presence of bile

salts or other surface-active agents with similar growth-inhibiting properties and able to ferment

lactose at 3537C with the production of acid, gas, and aldehyde within 2448 hours (WHO,

2008).

13

They are also oxidase-negative and non-spore-forming and display b-galactosidase activity.

Bacteria are responsible for most of the most devastating water-borne diseases. Of concern is the

E.coli which is a faecal bacteria usually secreted in large numbers through human faeces.

Under the WHO standards, drinkable water should not have any trace of indicator organisms

(coliform or E.coli bacteria).

2.4.3 Bacteriological standards

Bacteriological classification of treated water supplies is as follows (Kabete treatment procedures);

Class I Excellent- contains no coliforms and no E.coli.

Class II Satisfactory- contains 1 to 3 coliforms and no E.coli.

Class III Suspicious- contains 4 to 10 coliforms and no E.coli.

Class IV Unsatisfactory- contains more than 10 coliforms and no E.coli.

Class V Unsatisfactory- contains one or more coliforms and 1 E.coli or more.

It should be noted that treated water should be restricted to class 1 only.

2.5 Chemical Parameters

Many chemicals in drinking water are of concern only after an extended period of exposure. Where

water sources are likely to be used for long periods, chemical contaminants should be given greater

attention. This entails adding treatment processes or seeking alternative sources. The later has been

significantly preferred.

14

2.5.1 Hydrogen ion concentration (pH)

It is the measure of acidity or alkalinity of water. It is a measure of hydrogen ions [H+] expressed

by the function pH given by:

PH= -log10 = log10 (1/ [H+]

A value of 7 is the neutral value .Any value below 7 indicates acidity and any above 7 indicates

alkalinity. The range of natural pH in fresh waters extends from around 4.5 for upland water to

over 10.0 in waters where there is intense photosynthetic activity by algae. However, the most

frequently encountered range is 6.0 8.0.

In treatment and distribution systems, it is necessary to know the pH of water, because

a) Effectiveness of coagulants are highly dependent on pH (Ratnayaka, et al., 2009).

b) pH determines effectiveness of disinfection. More alkaline water requires a longer contact time

or a higher free residual chlorine level at the end of the contact time for adequate disinfection (0.4

0.5 mg/L at pH 68, rising to 0.60 mg/L at pH 89; chlorination may be ineffective above pH 9)

(WHO, 2004: Ratnayaka, et al., 2009).

c) pH is influential for control of solubility and rate of reaction of most of the metal species

involved in corrosion reactions. It is particularly important in relation to the formation of a

protective film at the metal surface. For some metals, alkalinity and calcium hardness also affect

corrosion rates (WHO, 2004). The optimum pH will vary in different water supplies according to

the composition of the water and the nature of the construction materials used in the distribution

system. It is usually in the range of 6.5 to 8 (WHO, 2004).

2.5.2 Hardness

Water that is considered hard is high in dissolved minerals, specifically calcium and magnesium.

As the concentration of these minerals increase, the water becomes harder. Other ions which occur

in relative low concentrations but are still responsible for water hardness are iron, manganese,

aluminium and zinc (Water hardness, 2013)

There is no health risks associated with hard water. On the contrary, people who take hard water

throughout their lifetime have a lower rate of cardiovascular disease.

15

However, there are problems associated with hard water, these include

Grey straining of washed clothes.

Scum on wash and bath water following use of soap or detergent.

Reduced lathering of soaps.

Build-up of scale on electric heating elements and boilers.

Reduced water flow in hot water distribution pipes due to scale build-up.

Accumulation of whitish- grey scale in tea kettles and other containers used to

boil water.

Table 1: Hardness

Concentration of CaCO3, mg/l Degree of hardness

0 50 Soft

50 100 Moderately soft

100 150 Slightly hard

150- Moderately hard

200-300 Hard

>300 Very Hard

Source: ( Ratnayaka, et al., 2009).

Low level of hardness can be easily removed by boiling. High degree of hardness is removed by

the addition of lime. This method has also the benefit that iron and manganese contents are

removed and suspended particles including micro- organism are also reduced.

2.5.3 Fluorides

Fluoride comes from minerals such as fluorspar but in some countries fluoride is artificially added

to water. When present in optimum concentration of 0.8 to 1.2mg/l (depending on water intake per

day), fluoride minimizes dental caries. However, when present in excess concentrations, it is

responsible for adverse effects starting from mild mottling of teeth (yellowish discoloration) (FCE

481lecture notes, 2013).

16

Over many years, fluoride can build up in peoples bones, leading to skeletal fluorosis

characterized by stiffness and joint pain. In severe cases, it can cause changes to the bone structure

and cause crippling effects. Infants and young children are most at risk from high amounts of

fluoride as their bodies are still growing.

2.5.4 Alkalinity

Alkalinity is the concentration of hydrogen ions that can be neutralized or the acid neutralizing

capacity of water. Alkalinity is a measurement of acid neutralizing capacity. It is the total

concentration of strong acid required to reduce the pH to an end point of say 4.5 (AWWA, 2011).

In natural water, pH is determined largely by the concentration of hydrogen ions and alkalinity by

the concentrations of hydroxyl, bicarbonate and carbonate ions in water. Other species often

present in small concentrations such as silicates, borates, ammonia, phosphates and organic bases

contributes for alkalinity (Dallas and Day, 2004).

Information concerning alkalinity is used in the following ways in practice.

a) Chemical Coagulation

Chemicals used for coagulations in conventional treatment system are usually metallic salts that

have acidic character. When dosed into water, the formation of hydroxide floc is the result of the

reaction between the acidic coagulant and the natural alkalinity of the water, which usually consists

of calcium bicarbonate. The hydrogen ions released react with the alkalinity of the water. If the

raw water has insufficient alkalinity or buffering capacity, additional alkali such as hydrated

lime, sodium hydroxide, or sodium carbonate must be added. Thus, the alkalinity acts to buffer the

water in a pH range where the coagulant can be effective. For effective and complete coagulation

to occur, alkalinity must be present in excess of that destroyed by the acid from the coagulant

(Ratnayaka, et al., 2009).

b) Water Softening

Water softening is a removal of calcium, magnesium, and other polyvalent cations, including

Ba2+, Sr2+, Fe2+, and Mn2+, achieved through cation exchange with addition of lime and soda

ash. Alkalinity is a major item that must be considered in calculating the lime and soda ash

requirements in softening of water by precipitation methods. The alkalinity of softened water is a

consideration in terms of whether such waters meet drinking water standards ( Ratnayaka, et al.,

2009).

17

c) Corrosion Control

Many factors determine whether water will be corrosive but three specific characteristics are

important (Ratnayaka, et al., 2009):

i. Low pH value, i.e. acidity;

ii. High free carbon dioxide (CO2) content; and

iii. Absence or low amount of alkalinity.

To control corrosion in water distribution networks, the methods most commonly applied are

adjusting pH, increasing the alkalinity and/or hardness or adding corrosion inhibitors, such as

polyphosphates, silicates and orthophosphates (WHO, 2004). Alkalinity must be known in order

to calculate the Langelier saturation index that measures the corrosiveness of water.

d) Buffering

Alkalinity is important for fish and aquatic life because it protects or buffers against rapid pH

changes. Aquatic organisms are sensitive to pH change of water. Few aquatic organisms tolerate

waters with pH less than 4 or greater than 10 (Dallas and Day, 2004).

Higher alkalinity levels in surface waters will buffer acid rain and other acid wastes and prevent

pH changes that are harmful to aquatic life.

There are three kinds of alkalinity referred to in environmental literature. Phenolphthalein

alkalinity, methyl orange alkalinity, and total alkalinity (Sawyer, et al., 2003).

1. Phenolphthalein alkalinity: A measure of concentrated acid required to reduce a base as strong

as or stronger than the carbonate ion. If the sample water has a pH level higher than approximately

8.3, you will see two equivalence points in the titration curve instead of just the one around 4.5.The

first drop in pH at around 8.3 is the phenolphthalein equivalence point, and the amount of acid

used to titrate to this point is used to calculate the phenolphthalein alkalinity. If the sample water

is initially below pH 8.3, the phenolphthalein alkalinity is zero.

2. Methyl orange alkalinity: A measure concentrated acid required to reduce a base as strong as,

or stronger than the bicarbonate ion. This is calculated using the volume of acid needed to titrate

to the lower pH equivalence point of 4.5.

3. Total alkalinity: The sum of the phenolphthalein alkalinity and the methyl orange alkalinity.

18

2.6 Surveillance and Monitoring

Surveillance is an investigative activity undertaken to identify and evaluate factors associated with

drinking water which could pose a risk to health. Therefore, there is protection of public health by

promoting improvement of the quality of water supplies. A surveillance agency is responsible for

independent (external) surveillance through periodic audit of all aspects of safety and verification

testing. Water quality monitoring is the foundation on which water quality management is based

(Bartram and Balance, 1996).

International standards (WHO)

National standards (KEBS)

WASREB

WASREB ensures that surveillance and monitoring is done by the Water Service Providers. WSP

are liable to the health and dissatisfaction of consumers. Reports should also be made to Water

Service Boards.

19

Currently, water quality sampling and testing is conducted at sources, treatment plants, storages

and distributions by the Water Quality Assurance Department of the Nairobi City Water and

Sewerage Company (NCWSC). The objective of sampling and testing is for compliance with

established standards. Sampling and testing is also conducted at the request of customers or when

there is complaint from customers with respect to water quality.

Under the WHO guidelines on, water quality standards, there should be separate roles in

monitoring by the WSP and an independent regulating body.

Monitoring of the water control measures includes;

Temperature of remote areas that is done frequently e.g. weekly.

Disinfectants and pH usually employed weekly or monthly.

Microbial quality of water especially following system maintenance or repairs.

However, daily monitoring is necessary in the presence of suspected water related cases of human

illness. For recently commissioned or following maintenance of the system, monitoring of drinking

water quality is required to be more frequent. This should be done until the water quality has

stabilized.

2.6.1 Monitoring programs

According to WASREB quality guidelines, monitoring program involves some surveillance

mechanisms that include;

a) Self-monitoring

Self-monitoring is undertaken by WSP in accordance with sampling schedule. The monitoring in

the sampling schedule are the minimum self-monitoring frequencies that must be performed;

however the provider may choose to perform monitoring at a greater frequency than specified if

so desired.

20

Schedule 1: WSP Sample Schedules for Water Quality Monitoring

Name of Water Service Provider:

Category:

System description:

Water production to town (m3/yr.)

Number of separate networks

Include layout showing sampling points in

the system.

Network 1

description

Number of tests

planned according to

guideline

Number of tests

conducted

Number of tests

within standard

Residual chlorine

Bacteriological

Turbidity, pH,

colour

Other

physiochemical

Source: (WASREB)

21

b) Scheduled monitoring

Scheduled monitoring involves the systematic sampling and inspection by the WSB in accordance

with a predetermined schedule. Scheduled monitoring will serve to check for compliance with the

requirements.

c) Unscheduled monitoring

Unscheduled monitoring is instituted by the WSB to provide a less formal type of surveillance on

the provider. Similarly, WASREB can undertake unscheduled monitoring to check water

compliance by the WSPs and WSBs.

d) Demand monitoring

The WSP conducts demand monitoring when an upset or other disruption of system operation

occur. In addition, the WSB and WASREB depending on the severity of the occurrence can

undertake demand monitoring as and when required.

2.7 Sampling

2.7.1 Sample collection

When water samples are collected for analysis, care should be taken to ensure that there is no

external contamination of the samples. In order to minimize inconsistencies and ensure the

accuracy of the process, it is recommended that the sampling should be done by qualified persons

(WASREB).

Glass bottles are considered the best for sampling with a capacity of at least 200ml. They should

have securely fitting stoppers or caps with nontoxic liners and both bottles and liners should be

sterilized. Avoid cotton wool plugs or paper caps as they tend to fall off during sampling and

increase the risk of contamination. Bottles can be reused to minimize costs but after they have been

desterilized.

22

Whenever chlorine is used for disinfection, a chlorine residual may be present in the water after

sampling and will continue to act on any bacteria in the sample; the results of the microbiological

analysis may therefore not be indicative of the true bacteriological content of the water. To

overcome this difficulty, it is common procedure to add sodium thiosulfate to the sample, which

immediately inactivates any residual chlorine but does not affect the microorganisms that may be

present. The sodium thiosulfate should be added to the sample bottles before they are sterilized.

For 200-ml samples, four or five drops of aqueous sodium thiosulfate solution (100 g/litre) should

be added to each clean sample bottle (WHO, 1997).

2.7.2 Sampling from a tap

1.0 Clean the tap. Remove from the tap any attachments that could cause splashing. Use a clean

cloth and wipe the outlet to remove any dirt.

2.0 Open the tap. Turn on the tap and let the water run for at least one minute. The tap should

be left to run at maximum flow.

3.0 Sterilize the tap. Sterilize the tap for a minute with the flame from a gas burner, cigarette

lighter, or an ignited alcohol-soaked cotton wool swab.

4.0 Open the tap before sampling. Turn on the tap and allow flow for at least a minute at

medium flow. Care should be taken not to adjust flow after it has been set.

5.0 Filling sterilized bottle. Carefully unscrew the cap or pull out the stopper of the bottle.

While holding the cap and protective cover face downwards, immediately hold the bottle

under the water jet and fill. A small air space should be left to make shaking before analysis

easier. After placing a stopper or screwing on the cap, fix a brown paper protective cover

in place with a string.

Table 2: Minimum sample numbers for piped drinking-water in the distribution system.

Population served No. of monthly samples

100000 1 per 10 000 population, plus 10 additional

samples

Source: (WHO, 1997).

23

2.7.3 Sampling points

The Drinking Water Quality and Effluent Monitoring Guideline established by Water Services

Regulatory Board has set clear that strategic sampling points should be identified within a

distribution system to ensure that they are representatives of the entire system and at the same time

ensuring that particular problem areas are identified.

Sampling points should include the most unfavourable sources or places in the supply system

particularly points of possible contamination such as unprotected sources, loops, reservoirs, low-

pressure zones and ends of the system.

For a given network, sampling points should be uniformly distributed throughout a piped

distribution system, taking population distribution into account; the number of sampling points

should be proportional to the number of links or branches. The samples should be representatives

of the different sources from which water is obtained by the consumers or enters the system.

In systems with more than one water source, the locations of the sampling points should take into

account of the number of inhabitants served by each source (WHO, 1997).

2.8 Health implications

According to WHO, 2008, the principal risks to human health associated with the consumption of

polluted water are microbiological in nature. However the importance of chemical contamination

should never be underestimated. Widespread health risk associated with drinking-water is

contamination, either directly or indirectly, by human or animal excreta, particularly faeces. If

such contamination is recent, and if those responsible for it include carriers of communicable

enteric diseases, some of the pathogenic microorganisms that cause these diseases may be present

in the water. Drinking the water, or using it in food preparation, may then result in new cases of

infection. An estimated 80% of all diseases and over one-third of deaths in developing countries

are caused by the consumption of contaminated water and on average as much as one-tenth of each

persons productive time is sacrificed to water-related diseases.

Through epidemiological investigations, it is evident that all aspects of the water supply services

influence health, so do hygiene behaviours and sanitation. The provision of safe drinking-water is

the most important step which can be taken to improve the health of a community by preventing

the spread of waterborne disease.

24

Microbiological monitoring provides a sensitive indication of the extent to which source

protection, treatment, and distribution are effective barriers to the transmission of infectious agents

of waterborne disease at the time that the samples were taken. It is important to realize at the outset

that microbiological integrity is provided by source protection and treatment, and that sudden loss

of this integrity or steady deterioration may be missed if monitoring is not frequent enough.

It is difficult with the epidemiological knowledge currently available to assess the risk to health

presented by any particular level of pathogens in water, since this will depend equally on the

infectivity and invasiveness of the pathogen and on the innate and acquired immunity of the

individuals consuming the water. It is only prudent to assume, therefore, that no water in which

pathogenic microorganisms can be detected can be regarded as safe, however low the

concentration. Furthermore, only certain waterborne pathogens can be detected reliably and easily

in water, and some cannot be detected at all.

Over many years, a universal agreement was adopted on the concept of faecal indicator species as

the most specific and suitable bacteriological indicator of faecal pollution is the Escherichia coli.

Any water that contains E. coli must be regarded as faecally contaminated and unsafe, and

requiring immediate remedial action.

Only strict attention to source protection and to the design and operation of efficient treatment and

distribution will guarantee the exclusion of pathogens from drinking-water delivered to the

consumer. For each water supply, the quality of the source water must guide the selection of the

treatment processes, and due attention must be given to the ability of these processes to eliminate

different pathogens.

25

WHO drinking water guidelines

Table 3: WHO drinking water guidelines

Parameter Unit WHO guideline

pH pH scale 6.5 to 8.5

Odour and Taste Not objectionable

Colour TCU

26

Kenya Bureau of Standards (KEBS) Guidelines

i. Bacteriological quality

Kenya Drinking Water Quality Standards, KS 150-1996 that conforms to WHO guideline limits.

Table 4: Microbiological limits for drinking water and containerized water.

Type of microorganisms Drinking water Containerized water

Total viable counts at 370C

per ml (max)

100 20

Coliforms in 250ml Shall be absent Shall be absent

E.coli in 250ml Shall be absent Shall be absent

Staphylococcus aureus in

250ml

Shall be absent Shall be absent

Sulphite reducing anaerobes

in 50ml


Pseudomonas aeruginosa

fluoresence in 250ml


Streptococcus faecallis Shall be absent Shall be absent

Shigella in 250ml Shall be absent Shall be absent

Salmonela in 250ml Shall be absent Shall be absent

27

ii. Desirable Aesthetic Quality

Table 5: Aesthetic Quality for Requirements of Drinking water and Containerized water (KS 150

and WHO Guidelines).

Substance or characteristic Drinking water Containerized water

Colour in TCU (max) 15 15

Taste and colour Shall not be offensive to

consumers

Shall not be offensive to

consumers

Suspended matter nil nil

Turbidity in NTU (max) 5 1

Total dissolved solids (mg/l)

max

1500 1500

Hardness as CaCO3(mg/l)

max

500 500

Aluminium as Al, mg/l 0.1 0.1

Chloride as Cl, mg/l (max) 250 250

Copper as Cu, mg/l (max) 0.1 0.1

Iron as Fe, mg/l (max) 0.3 0.3

Sodium as Na, mg/l (max) 200 200

Sulphate as SO-42, mg/l (max) 400 400

Zinc as Zn, mg/l (max) 5 5

pH 6.5 to 8.5 6.5 to 8.5

Magnesium as Mg, mg/l

(max)

100 100

Chlorine concentration as Cl,

mg/l

0.2-0.5 nil

Calcium as Ca, mg/l 250 250

Ammonia mg/l (max) 0.5 0.5

Fluorides mg/l, (max) 1.5 1.5

28

Water Service Regulatory Board (WASREB) Guidelines

Table 6: Aesthetic quality requirements for drinking water and bottled drinking water (adopted

from KS 05-459: Part 1:1996).

Substance or

characteristic

unit Drinking water Bottled

drinking water

Method of test

colour TCU 15 15 KS 05-459

Taste and colour Shall not be

offensive to

consumers

Shall not be

offensive to

consumers

KS 05-459

Suspended

matter

nil Nil KS 05-459

turbidity NTU, max 5 1 KS 05-459

Total dissolved

solids

mg/l max 1500 1500 KS 05-459

Hardness as

CaCO3

mg/l max 500 500 KS 05-459

Aluinium as Al mg/l max 0.1 0.1 KS 05-459 Chloride as Cl- mg/l max 250 250 KS 05-459

Copper as Cu mg/l max 0.1 0.1 KS 05-459

Iron as Fe mg/l max 0.3 0.3 KS 05-459

Manganese as

Mn

mg/l max 0.1 0.1 KS 05-459

Sodium as Na mg/l max 200 200 KS 05-459

Sulphate as SO4 mg/l max 400 400 KS 05-459

Zinc as Zn mg/l max 5 5 KS 05-459

PH 6.5 to 8.5 6.5 to 8.5 KS 05-459

Magnesium as

Mg

mg/l max 100 100 KS 05-459

Chlorine

concentration

Mg/l 0.2-0.5 Nil KS 05-459

Calcium as Ca mg/l max 250 250 KS 05-459

Ammonia (N) mg/l max 0.5 0.5 KS 05-459

Fluoride as F* mg/l max 1.5 1.5 KS 05-459

Arsenic as As mg/l max 0.05 0.05 KS 05-459

Cadmium as Cd mg/l max 0.005 0.005 KS 05-459

Lead as Pb mg/l max 0.05 0.05 KS 05-459

Mercury (Total

Hg)

mg/l max 0.001 0.001 KS 05-459

Selenium as Se mg/l max 0.01 0.01 KS 05-459

Chromium as Cr mg/l max 0.05 0.05 KS 05-459

Cyanide as CN mg/l max 0.01 0.01 KS 05-459

29

Phenolic

substances

mg/l max 0.002 0.002 KS 05-459

Barium as Ba mg/l max 1.0 1.0 KS 05-459

Nitrate as NO3 mg/l max 10 10 KS 05-459

Table 7: Microbiological limits for drinking water and containerized drinking water (Adopted

from KS 05-459: Part 1:1996).

Type of micro-

organism

Drinking water Containerized

drinking water

Method of test

Total viable counts at

370C, per ml, max

100 20 KS 05-200+

Coliforms in 250ml Shall be absent Shall be absent KS 05-200

E. Coli in 250ml Shall be absent Shall be absent KS 05-200

Staphylococcus

aureus in 250ml

Shall be absent Shall be absent KS 05-200

Sulphite reducing

anaerobes in 50ml


Pseudomonas

aeruginosa fl

uorescence

in 250ml


Streptococuus

faecalis


Shigella in 250ml Shall be absent Shall be absent KS 05-200

Salmonella in 250ml Shall be absent Shall be absent KS 05-200

30

2.9 Treatment and disinfection

According to the WHO guidelines for drinking water quality, this involves the ability to achieve a

guideline value within a drinking water supply. Collection, treatment, storage and distribution of

drinking-water involve deliberate additions of numerous chemicals to improve the safety and

quality of the finished drinking-water for consumers. In addition, water is in constant contact with

pipes, valves, taps and tank surfaces, all of which have the potential to impart additional chemicals

to the water. A qualitative ranking of treatment processes based on their degree of technical

complexity is as shown. The higher the ranking the more complex treatment.

2.9.1 Water treatment process

Water treatment involves physical, chemical and biological changes that are meant to transform

raw water into potable and wholesome waters. The specific treatment process used in any specific

case depends on the nature and quality of the raw water and the desired treatment water quality.

Thus, in many cases it is sufficient to only aerate and disinfect borehole water for domestic use.

Surface water on the other hand, due to pollution from various sources (sewage, industrial, bacteria

etc.) will usually nee full treatment which consists of coagulation / flocculation, sedimentation,

filtration and disinfection. In some cases especially where water of very high quality is required it

may be necessary to carry out more advanced treatment like adsorption with activated carbon. Yet

at other times methods for reducing the concentration of specific substances like fluorides may be

necessary.

Water treatment processes may be simple in nature, like sedimentation or may involve very

complex physiochemical changes, as in coagulation. The analysis carried out during water analysis

do not usually show how complex some of the physiochemical relationships in the water may be

and such analysis on its own may not reveal how much chemicals need to be added into the water

in order to achieve the desired results. The use of the jar test clearly illustrates this point. The actual

test procedures may also vary but the procedures given in the Standard Methods for the

Examination of Water and Waste Water (APHA) are well suited for most conditions (PHE lecture

notes 481).

31

Table 8: Ranking of technical complexity and cost of water treatment processes.

Ranking Examples of treatment processes

1 Simple chlorination

Plain filtration (rapid sand, slow sand)

2 Pre-chlorination plus filtration

Aeration

3 Chemical coagulation

Process optimization for control of DBPs

4 Granular activated carbon (GAC) treatment

Ion exchange

5 Ozonation

6 Advanced oxidation processes


In order to transform raw water, that contains coliform organisms, to potable water the

recommended treatment is as shown;

Table 9: Recommended treatment in relation to number of coliform organism per 100ml.

Coliform organism (Number/100ml). Recommended treatment.

0-50 Bacterial quality requiring disinfection only.

50-5000 Bacterial quality requiring full treatment

(coagulation, sedimentation, filtration and

disinfection only)

5000-50000 Heavy pollution requiring extensive treatment.

Greater than 50000 Very heavy pollution unacceptable as a source

unless no alternative exists. Special treatment

needed.


32

2.9.2 Chlorination

This method of disinfection is achieved through the use of pressurized liquefied chlorine gas,

sodium hypochlorite solution or calcium hypochlorite granules and on site chlorine generators.

They all dissolve in water to form hypochlorous acid (HOCL) and hypochlorite ion (OCL).

Different techniques of chlorination can be used including breakpoint chlorination, marginal

chlorination and super chlorination. Breakpoint chlorination is a method in which the chlorine dose

is sufficient to rapidly oxidize all the ammonia nitrogen in the water and to leave a suitable free

residual chlorine available to protect the water against reinfection from the point of chlorination to

the point of use. Super chlorination/dechlorinating is the addition of a large dose of chlorine to

effect rapid disinfection and chemical reaction, followed by reduction of excess free chlorine

residual. Removing excess chlorine is important to prevent taste problems. It is used mainly when

the bacterial load is variable or the detention time in a tank is not enough. Marginal chlorination is

used where water supplies are of high quality and is the simple dosing of chlorine to produce a

desired level of free residual chlorine. The chlorine demand in these supplies is very low, and a

breakpoint might not even occur.

Chlorination is employed primarily for microbial disinfection. However, chlorine is an oxidant

that can remove or assist in the removal of some chemicals for example decomposition of easily

oxidized pesticides such as aldicarb or oxidation of dissolved species to more easily removable

forms (e.g., arsenite to arsenate).

A disadvantage of chlorine is its ability to react with natural organic matter to produce THMs and

other halogenic DBPs. However the by-product formation may be controlled by optimization of

the treatment system (WHO, 1997).

Other disinfection methods include Ozonation, the use of chlorine dioxide, UV radiation and

advanced oxidation processes

33

Chapter Three

Methodology

3.1 Introduction

This entails the experimental data through description of methods and techniques used in collection

of data, analysis and experimentation which helps in accomplishing the projects objectives being

assessed of the water quality. The approach of the study was to sample points and establish whether

the various water parameters conform to the WHO, KEBS and WASREB standards.

3.2 Study area

The objective of the surveillance is to assess the quality of the Water Service Providers (WSP).

The sampling points are random, fixed and recognized by the Water Service Provider as genuine.

For this reason they are more likely to identify any and detect any local problems such as cross

connections and contaminations from leaking distribution system. Data was collected in the month

of February 2016.

Criteria for selecting sampling locations was based on the functional and recognized points used

by WSP. These points can be used to establish the quality of water in the University since the

selected points are representations of water quality monitoring in the area. Points selected are areas

around the University of Nairobi and are as listed below:

Central park.

Serena hotel.

Nairobi primary school.

Metropolitan estate.

Boulevard hotel.

34

Figure 3:Sampling points around the University environs.

Figure 4:Sampling points in Nairobi County

35

3.3 Limitations of the study

1. Water quality monitoring was conducted for the month of February due to time limit and

delayed permits from the Water Service Providers. However, it is required that water

quality monitoring be done at least on monthly basis.

2. All the laboratory water quality parameters were conducted under the constraint of the

available equipment at the University of Nairobi Public Health Laboratories (Hyslop

building). One of the highlight parameters left out was the bacteriological test. None of the

coliform counts or the E.coli test was conducted.

3. Comparison of data obtained from both the NCWSC Kabete treatment works and the UON

laboratories may have been different due to the different technologies of the equipment

used.

4. There was missing water quality data, as well as inconsistent sampling frequency. The

report is based on available data obtained from Water Quality Department of NCWSC.

3.4 Sampling

The minimum number of samples that were collected were in accordance to WASREB

requirements. For each sampling point, one sample was collected to represent a population of

5,000.

Field tests of residual chlorine were done to reduce the effect of light on the sample hence

increasing the accuracy of the final result. The chlorine in water sample is affected by illumination

from sunlight during transport to the lab.

All the sampling bottles were provided by the University of Nairobi and were fully disinfected and

cleaned with distilled water. To obtain the samples, care was observed to give true representation

of the existing conditions and handled in such a way to prevent deterioration and contamination

before arriving at the laboratories. Each sample was correctly and clearly marked with a permanent

marker and the point of collection noted.

36

3.5 Laboratory tests

After sampling, the laboratory tests were categorised as follows:

Physical tests.

Chemical tests.

Bacteriological examination.

The tests carried are in accordance to those proposed by WASREB to the WSP on monthly basis

(Schedule, appendix).

3.5.1 Physical tests conducted

They included;

Turbidity (Turbidimeter).

Colour (Lovibond comparator).

Temperature.

Total dissoved solids.

3.5.2 Chemical tests conducted

The chemical tests conducted include;

pH (pH meter).

Residual chlorine (N N-diethyl-p-phenylenediamine, DPD tablet).

Conductivity

Hardness

Fluorides.

Total coliforms and E.coli bacterial contamination tests were done at Kabete Treatments

Works Laboratory since the UON . Two methods were incorporated namely the presence

absence test and the M.P.N. test. However, WHO (1997), recommends presence-absence tests

for monitoring good quality drinking water where positive results are known to be rare.

Further, treated water containing residual chlorine kills present bacteria in the water. MPN test

was also done to determine the exact total coliform and E.coli numbers.

37

3.6 Questionnaire

Coordinator Nairobi water treatment labs (Kabete).

How is the treatment process carried out?

How often is sampling of piped water carried out?

In case of vehicle or machine breakdowns, what are the contingency plans?

How do you deal with pipe bursts in areas prone to contamination (sewer lines and dump sites)?

How can clients/customers contact you in case they are not satisfied with the quality of water

supplied to them?

...

38

Chapter Four

Results and Analysis

Results were summarized in two categories as follows:

Category A which represents experiments that I, (Gatimu, project student), conducted

(P.H.E. labs).

Category B which represents experiments conducted by WSP (Kabete treatment labs).

Physical Parameters

Parameters

1 2 3 4 5

WHO

KEBS

Serena

Hotel

Central

Park

Boulevard

Hotel

Metropolitan

Estate

Nairobi

Primary

School

W

A

S

R

E

B

A B A B A B A B A B

Colour(TCU) 5 0 5 0 5 0 5 0 5 0 < 15 < 15 <

1

5

Turbidity(NTU) 1 1.4 0.9 1.23 1.1 1.39 0.9 0.5 0.6 0.5 < 5 < 5

Documents

UNIVERSITY OF NAIROBI PROJECT