Murithi M - Purification of Well Water in Juja

7/26/2019 Murithi M - Purification of Well Water in Juja

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PURIFICATION OF WELL WATER IN JUJA USING

LOCAL NATURAL MATERIALS

AUTHOR

E25-0136/04MICHAEL MURITHI

PROJECT SUPERVISOR

MR. MWANGI

CIVIL, CONSTRUCTION AND ENVIROMENTAL ENGINEERING DEPARTMENT

APRIL 2010

This project is submitted as a partial fulfillment of the award of degree in Bsc. civil Engineering, JKUAT


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DEDICATION

To my Sis and Dad for their support and concern.I give praise to God almighty.

A man with one watch knows what time it is. A man with two is never quite sure.- Anonymous

Your saw my body. In your book they were all written, the days that were ordained for me, when as yet

there was none of them. How precious also are thy thoughts unto me, O God! How great is the sum of

them! How precious to me are your thoughts, God! How vast is the sum of them! If I should count them,

they are more in number than the sand: When I awake, I am still with thee. Ps 139:16-17


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ACKNOWLEDGMENT

I would like to express my sincere gratitude to those that have assisted and supported me and made this

project possible. I wish to appreciate the Almighty God for His strength, provision and protection during

this project period. My supervisor Mr. Mwangi, who guided, advised, spent his time and assisted me in

giving my best to this project.

The department of civil, construction and environmental engineering was of great help to me in providing

materials, administrative and technical support; say Mr. Karugu, Mr. Kibe and Mr. Munyi.

Jennifer, food science technician who was ever available to assist me in lab tests.

My classmates, friends, Mitambo, Sam, roommate-Deno and dad deserve more than an appreciation for

providing resources, advice and lively moments that made this journey worth finishing. May God bless

you abundantly.


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DECLARATION

I hereby declare that the research work compiled herein is my original work and has not been done

anywhere else to the best of my knowledge.

Any duplication or translation of this work beyond that permitted by the relevant copyright laws, without

permission from the author is unlawful.

Signature .. Date ..

AUTHOR

CERTIFICATION

I have read this report and approve it for examination.

Signed (Supervisor) Date.

Mr. G.M. Mwangi


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ABSTRACT

The Kenyan government is responsible for supplying treated water to its citizen. The Water Act 2002

and the Public Health Act in Kenya call for a focus on sanitation due to the knowledge of the dire

consequences that result from inadequate attention-health crisis. However the government effort to supply

each household with clean piped water has not been achieved.

This study sought to present findings on use of Pumice, sand, sunlight and quarry dust as alternative

means of water purification. UV light is efficient in killing micro organisms. These materials were

arranged in a PVC column and used to filter the water. This water was then exposed to sunlight for up to

6 hours. Turbidity ,E coli, total dissolved solids, total suspended solids, chemical oxygen demand COD,

biochemical oxygen demand BOD, Ph, nitrite and ammonia were used as parameters to monitor

efficiency of the media. The set up was efficient in removal of total suspended solids, total dissolved

solids and Escherichia coli (91.95, 73.04, and 86.80% respectively). Turbidity removal efficiency by the

column unit was poor (64.02%).However after 6h of sunlight treatment, turbidity reduced by 33.35%

resulting to overall efficiency of 76.02%. E coli were not completely eliminated by sunlight due to

turbidity in the filtrate. Percentage removal of nitrite by the set up was 25%.Ammonia was absent in the

filtrate. Hence sand, quarry dust and pumice can effectively purify well water.


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TABLE OF CONTENTS

DEDICATION i

ACKNOWLEDGMENT ii

DECLARATION iii

ABSTRACT iv

TABLE OF CONTENTS v

LIST OF FIGURES viii

LIST OF TABLES ix

1.0 INTRODUCTION 1

1.2 PROBLEM STATEMENT AND JUSTIFICATION 2

1.3 RESEARCH OBJECTIVE 2

1.3.1 Specific objectives 2

1.4 RESEARCH HYPOTHESIS 3

1.5 LIMITATION OF STUDY 3

2.0 LITERATURE REVIEW 4

2.1 INTRODUCTION 4

2.2 TYPES OF WATER WELLS 4

2.3 WATER POLLUTANTS 5

2.4 ENVIRONMENTAL PROBLEMS AND MITIGATION 6

2.5 WATERBORNE DISEASES 7

2.6 LOCAL MATERIALS 7

2.6.1Pumice 7

2.6.2 Sand 7

2.6.2.1Effect of sand size on removal of bacteria 8

2.6.2.2 Effect of sand depth on turbidity and color removal 8

2.6.2.3Effect of sand depth on bacteriological quality and removal of Cryptosporidium oocysts 10

2.7 TYPES OF TESTS 11

2.7.1 Turbidity 11


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2.7.1.1 Turbidity Test 11

2.7.2 PH 12

2.7.2.1 Applications 12

2.7.3 Sieve Analysis Test 12

2.7.3.1 Need and Scope 12

2.7.3.2 Apparatus Required 13

2.7.4 E. COLI TEST 13

2.7.5 BIOCHEMICAL OXYGEN DEMAND 13

2.7.6 CHEMICAL OXYGEN DEMAND 13

2.7.7 TOTAL DISSOLVED SOLIDS (TDS) 14

2.7.8 TOTAL SUSPENDED SOLIDS (TSS) 14

2.7.9 COLOUR 14

2.8 THE FILTRATION PROCESS 15

2.8.1FILTER CONTROL 16

2.8.1.1 Rate of flow controllers 17

2.9 FLOW RATE 17

2.9.1Effect of flow rates on bacteriological quality turbidity and colour removal 18

2.10 DARCY'S LAW 1

2.11. BIOSAND FILTERS 21

2.11.1 Biosand technologies 21

2.11.3 Benefits & Drawbacks 23

2.11.4 Biosand filters in Congo 23

2.11.4 The impact of biosand filters 23

3.0RESEARCH METHODOLOGY 25

3.1EXPERIMENTAL SET UP 25

3.1.1 Column unit 26

3.1.2. Column set up and media packing 26

3.2 SIEVE ANALYSIS PROCEDURE 28

3.3 SAMPLING PROCEDURES 28

3.3.1Sampling 28


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3.3.2Handling and treatment of sample 28

3.4 LABORATORY TESTS 2

3.5 DATA ANALYSIS 2

3.6 DESIGN OF THE COLUMN UNIT 30

4.0 EXPERIMENTAL RESULTS AND DISCUSSION 31

4.1 RESULTS 31

4.1.1 Water Quality in wells 31

4.2 Water quality after filtration 33

4.2.1 Filtrate from column unit (tap 1) 33

4.2.2 Filtrate after sunlight treatment (tap 2) 34

4.3 GRAPHS 35

4.5 Efficiency of the set up 40

5.0 CONCLUSION 42

5.1 RECOMMENDATIONS 42

6.0 REFERENCES 43

6.1 TABLES AND PLATES 45


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LIST OF FIGURES

Figure 1.2 Marshy water around a well in Juja. 2

Figure 2.2 A hand dug well 4

Figure 2.3 Littered areas next to a well. 5

Figure 2.7.1 turbid water. 11

Figure 2.7.3.2 set of sieves 13

Figure 2.11.1: Biosand filter 21

Figure 2.11.2: use of biosand filter 22

Figure 3.1.2 a fabricated filter column outside structures lab, JKUAT. 26

Figure 3.2: Mike sieving sand 28

Figure 3.3: collecting a sample from a well 28

Figure 3.4: lab test of a sample 2

Figure 4.4: filtered and unfiltered samples 40


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LIST OF TABLES

TABLE1: Effect of effective size (D10) on filter performance at filtration rate of 0.1 m/hr...................... 8

TABLE 2: Effects of sand bed depth on filter performance (a) Filter 1: (ES=0.20 mm)...........................

3.5 ........................................................................................... 2

Table 4.1.1: Results of the data collected from Juja wells.......................................................................... 31

4.2.1 1 .......................................................................................... 33

4.2.2 ( 2). ................................................................. 34

4.4 . .............................................................................................................. 41

WHO DRINKING WATER GUIDELINES .............................................................................................. 45


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1

1.0 INTRODUCTION

1.1 PROBLEM BACKGROUND

Water pollution is a major problem in the global context. It has been suggested that it is the leading

worldwide cause of deaths and diseases, and that it accounts for the deaths of more than 14,000 people

daily. In addition to the acute problems of water pollution in developing countries, industrialized

countries continue to struggle with pollution problems as well. Municipalities and industries sometimes

discharge waste materials into bodies of water that are used as public sources of supply. Surface run-off

also brings mud, leaves, and decayed vegetation together with human and animal wastes into streams and

lakes. In turn, these organic wastes cause algae and bacteria to flourish. Toxic bacteria, chemicals and

heavy metals routinely infiltrate and pollute our shallow wells making people sick while exposing them to

long term health consequences such as liver damage, cancer and other serious conditions. (Water

pollution-WIKIPEDIA, 2009)

Safe, clean drinking water and sanitation facilities are key to economic development and public health

in Kenya. Yet many Kenyans continue to have inadequate access to water, drink unsafe water, live near

open sewage and as a result suffer and die from water-borne diseases, which account for 60% of all

diseases in Kenya. Without a strategy to deal with this situation, rapid urbanization and population growth

mean worsening conditions for millions of Kenyans, especially the poorest. Recognizing this problem,

both donor agencies and the Government of Kenya (GoK) support reforms in the water/sanitation sector.

In particular, through the Water Act 2002, the GoK now encourages greater community initiative in

provision of services as well as the formation of publicly accountable local water and sewerage

companies (Columbia University, 2007). Based on Nairobis growth rate of 7.3 %( UON, 2005) and of

JKUAT student population, Juja increasingly serves as a residential base for those who work in Nairobi,

Githurai and study in JKUAT. This has placed high pressure on public services, notably on water and

sanitation delivery. As a result, provision of safe water to a majority in the area has depended primarily

upon the construction of wells and protection of spring discharge. The presence of poorly designed pit

latrines as well as poor and inadequate groundwater protection has led to contamination of spring water

and shallow water wells posing a risk of an outbreak of water borne diseases especially diarrhoea and

typhoid.


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1.2 PROBLEM STATEMENT AND JUSTIFICATION

In the absence of a sewer system, septic tanks and wells have been built without consideration for

public health outcomes. For example, pit latrines or septic tanks are too closely spaced to shallow wellscreating a situation in which the water supply becomes contaminated. Moreover there are no

predetermined water withdrawal points by the government, these points are chosen by the community and

theres no way of dealing with epidemics of mass water pollution in case of an outbreak.

Data from medical laboratories in the area (heartfelt pharmacy, 2009) show increased cases of typhoid

and amoebiasis in the months of September and October 2009.

A cross sectional water analysis showed presence of contamination in

some wells. I.e. E coli, nitrite.

Some of the wells in the area of study, JUJA are not currently in use.Those that are functional are not used for the purposes they were

intended for and are located in unhygienic environment (fig 1.2).

Residents are limited to using this water for washing and irrigation.

Some boreholes in JKUAT have excessive minerals (estates

department, 2009).

1.3 RESEARCH OBJECTIVE

The aim of this project is to evaluate removal rates of pollutants from shallow wells in Juja using local

natural materials namely pumice, sand and quarry dust.

1.3.1 Specific objectives

Design and fabrication of a filtering column.

Evaluate the efficiency of the filtering column in the removal of pollutants.

Evaluate the efficiency of sunlight in the removal of pollutants.

Figure 1.2 Marshy water around

a well in Juja.


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1.4 RESEARCH HYPOTHESIS

The local materials to be used will eliminate the biological pollutants from the water samples.

Some wells may have more pollutants while others may have none.

The water samples are contaminated by biological pollutants only.

1.5 LIMITATION OF STUDY

Time to collect and test the samples could be little.


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2

2.0 LITERATURE REVIEW

2.1 INTRODUCTION

Water well is an excavation or structure created in the ground by digging, driving, boring or drilling to

access groundwater in underground aquifers. The well water is drawn by pumps. It can also be drawn up

using containers, such as buckets, which are raised mechanically or by hand. Wells vary greatly in depth,

water volume and water quality. Well water typically contains more minerals in solution than surface

water and may require treatment to soften the water by removing minerals such as arsenic, iron and

manganese. (Wikipedia-water pollution, 2009)

2.2 TYPES OF WATER WELLS

1) Dug wells

Until recent centuries, all artificial wells didnt have pumps, and were dug wells of varying degrees of

formality. Their indispensability has produced numerous literary references, literal and figurative, to

them, including the Christian Bible story of Jesus meeting a wom

an at Jacob's well (John 4:6) and the "Ding Dong Bell" nursery rhyme about a cat in a well.

a) Hand dug wellsprovide a cheap solution to accessing ground water in rural locations, with a high

degree of community participation. They have been successfully excavated to 60m. They are cheap

(compared to drilling) as they use mostly hand labor for construction, have low operational and

Figure 2.2 A hand dug well


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maintenance costs. Hand dug wells (fig2.2) can be easily deepened, if the ground water level drops, by

telescoping the lining further down into the aquifer. Since most of them exploit shallow aquifers, the well

may be susceptible to yield fluctuations and possible surface contamination.

b) Driven wellsmay be created in unconsolidated material with a "well point", which consists of ahardened drive point and a screen (perforated pipe). The point is simply hammered into the ground,

usually with a tripod and "driver", with pipe sections added as needed. A driver is a weighted pipe that

slides over the pipe being driven and is repeatedly dropped on it. When ground water is encountered, the

well is washed of sediment and a pump installed.

c) Drilled wellscan be excavated by simple hand drilling methods (augering, sludging, jetting, driven,

hand percussion) or machine drilling (rotary, percussion, down the hole hammer). Drilled wells can get

water from a much deeper level by than dug wells - often up to several hundred meters. Water wells

typically range from 20 to 600 feet (180 m), but in some areas can go deeper than 3,000 feet

(910 m).Drilled wells are usually cased with a factory-made pipe, typically steel or plastic/pvc. Two

classes of drilled-well types based on the type of aquifer which the well is completed in:

shallowor unconfined wells

deeporconfined wells(Wikipedia-water pollution,2009)

2.3 WATER POLLUTANTS

Figure 2.3 Littered areas next to a well.


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Water is typically referred to as polluted when it is impaired by anthropogenic contaminants and either

does not support a human use, like serving as drinking water, and or undergoes a marked shift in its

ability to support its constituent biotic communities, such as fish. Natural phenomena such as volcanoes,algae blooms, storms, and earthquakes also cause major changes in water quality and the ecological status

of water. Sources of surface water pollution are discharges from a sewage treatment plant, a factory, or

storm drains, litter (fig 2.3), and improper waste disposal.

Groundwater aquifers are susceptible to contamination from sources that may not directly affect surface

water bodies. Most of the bacteria, viruses, parasites and fungi that contaminate well water come from

fecal matter from humans and other animals. Common bacterial contaminants includeE. coli, Salmonella,

Shigella,and Campylobacter jejuni.Common viral contaminants include norovirus, sapovirus, rotavirus,

enteroviruses, and hepatitis A and E. Parasites include Giardia lamblia, Cryptosporidium, Cyclospora,

and microsporidia.

Chemical contamination is a common problem with groundwater.eg. Fertilizer, pesticides and volatile

organic compounds. Several minerals are also contaminants, including lead leached from brass fittings or

old lead pipes; chromium VI from electroplating and other sources; naturally occurring arsenic, radon and

uranium, all of which can cause cancer; and naturally occurring fluoride, which is desirable in low

quantities to prevent tooth decay, but which can cause dental fluorosis in concentrations above

recommended levels. Some chemicals are commonly present in water wells at levels that are not toxic,

but which can cause other problems. Calcium and magnesium cause what is known as hard water, which

can precipitate and clog pipes or burn out water heaters. Iron and manganese can appear as dark flecks

that stain clothing and plumbing, and can promote the growth of iron and manganese bacteria that can

form slimy black colonies that clog pipes. (Wikipedia-water pollution, 2009)

2.4 ENVIRONMENTAL PROBLEMS AND MITIGATION

A possible risk with the placement of water wells could be soil salination. This problem occurs when the

water table of the soil begins to drop and salt begins to accumulate as the soil begins to dry out.

Cleanup of contaminated groundwater tends to be very costly. Effective remediation of groundwater is

generally very difficult. Contamination of groundwater from surface and subsurface sources can usually

be dramatically reduced by correctly centering the casing during construction and filling the casing

annulus with an appropriate sealing material. Well water for personal use is often filtered. Deep bed sand


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filters are used extensively in drinking water and wastewater treatment. (Global Water Supply and

Sanitation Assessment 2000 Report)

2.5 WATERBORNE DISEASES

In developing countries four-fifths of all the illnesses are caused by water-borne diseases, with diarrhoea

being the leading cause of childhood death. The global picture of water and health has a strong local

dimension with some 1.1 billion people still lacking access to improved drinking water sources and some

2.4 billion to adequate sanitation. Today we have strong evidence that water-, sanitation and hygiene-

related diseases account for some 2,213,000 deaths annually.These diseases include

schistomiasis,Diarrhoea,malaria,Botulism,fluorosis

,poisoning,Lymphatic,methaemoglobinemia,polio,scabies,schistomiasis,trachoma,cholera and typhoid.

Water borne diseases spread by contamination of drinking water systems. (WHO 2000')

2.6 LOCAL MATERIALS

2.6.1Pumice

The properties of natural pumice were characterized including the microstructure, porosity,

mechanical strength, composition and harmful trace element content. The results show that the natural

pumice has a porous structure with a pore size ranging from 50 to 150m, an interconnective porosity of

80%, and a compressive strength of 1.72 0.12 MPa. The natural pumice is mainly composed of silicate,

and the content of harmful trace elements of arsenic (As), cadmium (Cd), and mercury (Hg) in the pumice

are less than 3ppm, whereas the content of plumbum (Pb) is less than 5ppm. (Xiyu Li et al, 2009).Pumice

is Resistant to temperature change and does not expand or contract with temperature change. This reduces

the possibility of cracking and structural damage. Pumice is strong yet lightweight. (Flue and chimney)

2.6.2 Sand

Sand, along with gravel, silt and clay are collectively known as sediment, and are produced by the

mechanical and chemical breakdown of rocks. Its composition is largely dependent on the source

material. Sand is rich in mineral composition e.g. quartz, rutile and zircon magnetite. It has a grain size of

0.1-2 mm (Yahoo, 2009). Well sorted sand has a higher permeability, and is suitable for drainage

materials and, especially pure quartz sand, for water filtration. Grain shape can either be angular, sub

angular or rounded. More angular sand is preferred for concrete manufacture, and well-rounded sand is

preferred for filtration sand. When using sand as a filter media two important factors play a role; sand

grain size and sand bed depth. Its recommended that the effective size of sand used for continually


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operated slow sand filters (COSSFs) should be in the range of 0.15 0.35mm (Schulz and Okun, 1984). It

should be preferably rounded, and free from any clay, soil or organic matter.

2.6.2.1Effect of sand size on removal of bacteria

Results from some studies have shown that there is scope for the relaxation of typical values that havebeen used as benchmarks of slow sand filter design. A study (Muhammad et al, 1996) done on coarser

sand found that the treatment efficiency (for removal of bacteria, turbidity and color) of slow sand filters

was not very sensitive to sand sizes up to 0.45mm, although a slight increase in treatment efficiency was

observed with decreasing sand size. See Table 1. Filters with sand sizes larger than 0.2mm up to 0.45mm

produce satisfactory quality water with the added advantage of a longer filter run. (Ellis, 1987). In an

intermittent sand filter column of 60cm sand, fine-grained sand columns (D10 0.16mm) effectively

remove oocysts under a variety of conditions while Coarse-grained media columns (D10 0.90mm) yield

larger numbers of oocysts. Factorial design analysis indicated that grain size was the variable that mostaffected the oocyst effluent concentrations in these intermittent filters. (Logan et al, 2001).

2.6.2.2 Effect of sand depth on turbidity and color removal

In slow sand filtration, the vertical height of the sand bed is important in terms of filtration efficiency.

This is because the existence of biological activity in a sand filter occurs at depths of up to 0.5m within a

sand bed. An increased sand bed depth is required for coarser sands so as to increase the depth of activity.

Turbidity and color removal efficiencies improve as bed depth increase beyond 0.4m.See table 2. This

shows that adsorption occurs throughout the filter column in purifying water. Consequently, a decrease in

TABLE1:

Effect of effective size (D10) on filter performance at filtration rate of 0.1 m/hr

Filter D10(mm)

Average % Removal

Fecal

Coliforms

Total

Coliforms

Turbidity Colour

Filter1

Filter2

Filter3

0.20

0.35

0.45

99.60

99.30

99.00

99.70

99.30

98.60

96.50

96.50

96.20

95.10

95.10

92.00


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sand bed depth causes a reduction in total surface area of the sand grains and ultimately total adsorption

capacity is reduced (Muhammad, et al, 1996)

TABLE 2:

Effects of sand bed depth on filter performance

(a) Filter 1: (ES=0.20 mm)

Sand bed depth

(m)

Average % Removal

Feacal Coliforms Total Coliforms Turbidity Colour

0.73

0.40

99.60

98.40

99.70

99.00

96.50

87.50

95.10

72.00

(b) Filter 1: (ES=0.35 mm)

Sand bed depth

(m)

Average % Removal

Fecal Coliforms Total Coliforms Turbidity Colour

0.73

0.40

99.30

97.40

99.30

98.70

95.50

86.50

95.10

72.00

(c) Filter 3: (ES=0.45 mm)

Sand bed depth

(m)

Average % Removal

Fecal Coliforms Total Coliforms Turbidity Colour

0.73

0.40

99.00

95.90

98.60

98.10

96.20

85.00

92.00

66.00


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2.6.2.3Effect of sand depth on bacteriological quality and removal of Cryptosporidium oocysts

Muhammad, et al (1996) concluded that most bacteriological purification occurs within the top 400mm of

a sand bed. They found that bacteriological treatment was not highly sensitive to sand bed depth (Table

2), suggesting that a continually operated slow sand filter bed could be reduced even further to 0.40m and

still produce a satisfactory bacteriological quality of water. Bacteria treatment efficiency becomes more

sensitive to depth with larger sand sizes because the total surface area within the filter is reduced in a sand

bed with larger grains, as well as higher flow rates. Research done by Logan et al (2001) on intermittent

sand filter columns of 60cm sand revealed that the depth of sand was also important in removal, and

became more important for coarser sands (D10 0.90mm). Filters with fine-grained sand that were run

under a variety of hydraulic loadings (4cm to 20cm) still had no oocysts deeper than the top 10-15cm of

sand. In comparison, in coarser-grained sand, oocysts were found at depths ranging from 20cm (4cm

hydraulic loading) to 60cm (10 and 20cm hydraulic loading).

In previous studies byBurhanettin Farizoglu, Alper Nuhoglu, Ergun Yildiz and Bulent Keskinler,sand

and pumice were used as a filtration media under rapid filtration conditions and performance results for

both were compared. Turbidity removal performance and head losses were investigated as functions of

filtration rate, bed depth and particle size. Under the same experimental conditions such as 750 mm bed

depth, 7.64m3/m2.h flow rate and, 0.51.0 mm grain size, turbidity removal rates for sand and pumice

were found to be 8590% and 9899%, respectively. The head loss for sand and pumice were found to be

460 mm and 215 mm, respectively. The results obtained have shown that pumice has a high potential for

use as a filter bed material.However this study did not evaluate use of these materials in removal offaecal coliform, total suspended solids, total dissolved solids, Ph, biochemical oxygen demand, and color.


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2.7 TYPES OF TESTS

2.7.1 Turbidity

Turbidity is the cloudiness or haziness of a fluid caused

by individual particles (suspended solids) that are

generally invisible to the naked eye, similar to smoke in

air(fig 2.7.1). In drinking water, the higher the turbidity

level, the higher the risk that people may develop

gastrointestinal diseases. This is especially problematic

for immune-compromised people, because contaminants

like viruses or bacteria can become attached to the

suspended solid. The suspended solids interfere with

water disinfection with chlorine because the particles act

as shields for the virus and bacteria. Similarly, suspended

solids can protect bacteria from ultraviolet (UV)

sterilization of water. (Turbidity, lenntech 2010)

The main impact is merely esthetic: nobody likes the

look of dirty water. But also, it is essential to eliminate the turbidity of water in order to effectively

disinfect it for drinking purposes. This adds some extra cost to the treatment of surface water supplies.

(Turbidity, lenntech 2010)

2.7.1.1 Turbidity Test

The Turbidity Test is designed to scientifically and objectively judge the solubility of a sample to the

solvent specified in Clarity of Solution in Purity in the individual monograph. The most widely used

measurement unit for turbidity is the FTU (Formazin Turbidity Unit). ISO refers to its units as FNU

(Formazin Nephelometric Units).

There are several practical ways of checking water quality, the most direct being some measure of

attenuation (that is, reduction in strength) of light as it passes through a sample column of water. The

alternatively used Jackson Candle method (units: Jackson Turbidity Unit or JTU) is essentially the

inverse measure of the length of a column of water needed to completely obscure a candle flame viewed

through it. The more water needed (the longer the water column), the clearer the water.

Figure 2.7.1 turbid water.


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A property of the particles that they will scatter a light beam focused on them is considered a more

meaningful measure of turbidity in water. Turbidity measured this way uses an instrument called a

nephelometer with the detector setup to the side of the light beam. More light reaches the detector if there

are lots of small particles scattering the source beam than if there are few. The units of turbidity from a

calibrated nephelometer are called Nephelometric Turbidity Units (NTU). (Lenntech, turbidity 2010)

2.7.2 PH

PHis a measure of the acidity or basicity of a solution. Pure water is neutral, either a very weak acid or

a very weak base (center on the pH scale), giving it a pH of 7, or 0.0000001MH+. Hydrogen ions in

water can be written simply as H+or as hydronium (H3O+) or higher species (e.g. H9O4

+) to account for

solvation, but all describe the same entity. However, pH is not precisely p[H], but takes into account an

activity factor, which represents the tendency of hydrogen ions to interact with other components of the

solution, which affects among other things the electrical potential read using a pH meter. As a result, pH

can be affected by the ionic strength of a solution. Solutions with a pH less than 7 are said to be acidic

and solutions with a pH greater than 7 are said to be basic or alkaline. (Wikipedia, pH 2010)

2.7.2.1 Applications

Pure water has a pH around 7; the exact values depend on the temperature. When an acid is dissolved in

water the pH will be less than 7 and when a base, or alkali is dissolved in water the pH will be greater

than 7. The measured pH values will mostly lie in the range 0 to 14. Since pH is a logarithmic scale a

difference of one pH unit is equivalent to a ten-fold difference in hydrogen ion concentration.

The pH of pure water decreases with increasing temperatures. Note, however, that water that has been

exposed to air is mildly acidic. This is because water absorbs carbon dioxide from the air, which is then

slowly converted into carbonic acid, which dissociates to liberate hydrogen ions. (Wikipedia, pH)

2.7.3 Sieve Analysis Test

The Standard grain size analysis test determines the relative proportions of different grain sizes as they

are distributed among certain size ranges.

2.7.3.1 Need and Scope

The grain size analysis is widely used in classification of soils. The data obtained from grain size

distribution curves is used in the design of filters for earth dams and to determine suitability of soil for

road construction, air field etc. Information obtained from grain size analysis can be used to predict soil

water movement although permeability tests are more generally used.


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2.7.3.2 Apparatus Required

Stack of Sieves including pan and cover

Balance (with accuracy to 0.01 g)

Rubber pestle and Mortar ( for crushing thesoil if lumped or conglomerated)

Mechanical sieve shaker

Oven

The balance to be used should be sensitive to the

extent of 0.1% of total weight of sample taken.

2.7.4 E. COLI TEST

E. coli bacteria have been commonly found in recreational waters and their presence is used to indicate

the presence of recent fecal contamination, but E. coli presence may not be indicative of human waste.

The units of e.coli are cfu/ml.

2.7.5 BIOCHEMICAL OXYGEN DEMAND

Biochemical oxygen demand is a measure of the quantity of oxygen used by microorganisms (e.g.,

aerobic bacteria) in the oxidation of organic matter. In this test, the dissolved oxygen level of a water

sample is measured five days after it was collected. On the day of collection, the DO level is measured in

an initial sample. The biochemical oxygen demand is the difference between DO levels in the two

samples. It is not a precise quantitative test, although it is widely used as an indication of the quality of

water. There are two recognized methods for the measurement of BOD: dilution and manometric

methods. (wikipedia.org/wiki/Biochemical_oxygen_demand)

2.7.6 CHEMICAL OXYGEN DEMAND

The chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic

compounds in water. Most applications of COD determine the amount of organic pollutants found in

surface water (e.g. lakes and rivers), making COD a useful measure of water quality. It is expressed in

Figure 2.7.3.2 set of sieves


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milligrams per liter (mg/L), which indicates the mass of oxygen consumed per liter of solution. Older

references may express the units as parts per million (ppm).

(wikipedia.org/wiki/Chemical_oxygen_demand) The basis for the COD test is that nearly all organic

compounds can be fully oxidized to carbon dioxide with a strong oxidizing agent under acidic conditions.

2.7.7 TOTAL DISSOLVED SOLIDS (TDS)

Total dissolved solids (TDS) is defined as the combined content of all inorganic and organic substances

contained in a liquid that are present in a molecular, ionized or microgranular suspended form. TDS is

measured on a quantity scale, either in mg/L or, more commonly, in parts per million (ppm). Simply put,

if the TDS level is 335 ppm, this means that out of one-million parts of H2O, 335 of those parts are

something else.

The Best method of measuring TDS is to evaporate a water sample and weigh the remains with a

precision analytical balance. This is the most reliable and accurate method. (Water testing 101: TDS)

2.7.8 TOTAL SUSPENDED SOLIDS (TSS)

Total suspended solids (TSS) gives a measure of the turbidity of the water TSS of a water sample is

determined by pouring a carefully measured volume of water (typically one litre; but less if the particulate

density is high, or as much as two or three litres for very clean water) through a pre-weighed filter of a

specified pore size, then weighing the filter again after drying to remove all water. The gain in weight is a

dry weight measure of the particulates present in the water sample expressed in units derived or calculated

from the volume of water filtered (typically milligrams per litre or mg/l). Although turbidity purports to

measure approximately the same water quality property as TSS, the latter is more useful because it

provides an actual weight of the particulate material present in the sample.

(adbio.com/science/analysis/tss.htm)

2.7.9 COLOUR

Impurities dissolved or suspended in water may give water different colored appearances. Dissolved and

particulate material in water can cause discoloration. Slight discoloration is measured in Hazen Units

(HU). Impurities can be deeply colored as well, for instance dissolved organic molecules called tannins

can result in dark brown colors, or algae floating in the water (particles) can impart a green color.

(wikipedia.org/wiki/Color_of_water)


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The color of a water sample can be reported as:

Apparent coloris the color of the whole water sample, and consists of color from both dissolved

and suspended components.

True coloris measured after filtering the water sample to remove all suspended material.

Water quality and color

The presence of color in water does not necessarily indicate that the water is not potable. Color-causing

substances such as tannins may be harmless. Color is not removed by typical water filters; however, slow

sand filters can remove color, and the use of coagulants may also succeed in trapping the color-causing

compounds within the resulting precipitate.In water with low turbidity, the apparent color corresponds

closely to the true color. However, if turbidity is high, the apparent color may be misleading.

(tpub.com/content/construction/14265/css/14265_274.htm)

2.8 THE FILTRATION PROCESS

The filter used in the filtration process can be compared to a sieve or micro strainer that traps suspended

material between the grains of filter media. However, since most suspended particles can easily pass

through the spaces between the grains of the filter media, straining is the least important process in

filtration. Filtration primarily depends on a combination of complex physical and chemical mechanisms,

the most important being adsorption. Adsorption is the process of particles sticking onto the surface of the

individual filter grains or onto the previously deposited materials. (OP filtration pdf).

In 1996 and with funding from UNCHS, SERVE began research on an appropriate slow sand filter for

use in households. A number of filters were designed and tested before a model was settled on. After

three months of testing with heavily polluted water the filter was removing 98% to 99% of all

contaminating organisms. A pre-filter is placed on top of the unit to remove most of the sediment. This is

a simple pan with small nail holes in the bottom to allow the water, but not the sand, to pass. The sand

from this filter can easily be removed and washed, protecting the larger filter. The slow sand filter

actually eats bacteria and viruses as they pass through. To do this, it grows algae on its surface. The

water must travel through a minimum of 75cm of sand to be effective. The outlet must also be above the

level of the sand to make sure it is always under water. Ordinary sand is used, though it needs very

thorough washing. The filter is made of galvanized tin readily available in the bazaar. Other materials

such as pottery could be used. Once a working design was settled on, several were placed in homes to see


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if there were social, cultural or other problems. Several improvements were suggested which are now

included into the design.(Brett Gresham,1996)

2.8.1FILTER CONTROL

Control of the filter operation requires the following equipment:

Rate of flow controller

Loss of head indicator

On-line turbidimeter


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2.8.1.1 Rate of flow controllers

Flow rates through filters are controlled by one of two different methods:

a) Declining rate

This method of control is used where the head loss through the plant is quite large. It allows the filter

head to increase until the filter becomes plugged with particles and the head loss is too great to continue

operation of the filter. The rate through the filter is much greater in the beginning of a filter run than at the

end when the filter is dirty. This method tends to be the most commonly installed in new filter plants.

This method is generally preferred because it requires less operator attention. (OP filtration pdf)

b) Constant rate

This type of control monitors the level of water on the top of the filter and attempts to control this level

from the start of the operation to the end. This is accomplished by the controller operating a valve on theeffluent of the filter. The valve will be nearly closed at the start of the filter run and fully open at the end.

This design is used when the head or pressure on the filter is limited. Both controllers consist of a venturi

tube or some other type of metering device as well as a valve to control the flow from the filter. In most

cases, the valve is controlled by an automatic control device, often an air-actuated type valve that is

controlled by the flow tube controller. (OP filtration pdf)

Loss of head indicator

As filtration proceeds, an increasing amount of pressure, called head loss across the filter, is required to

force the water through the filter. The head lossshould be continuously measured to help determine when

the filter has clogged. Usually the difference in the head is measured by a piezometer connected to the

filter above the media and the effluent line. (OP filtration pdf)

2.9 FLOW RATE

Flow rate in a sand column is proportional to the cross-sectional area of the sand and the pressure head

(hydraulic loading) of water on top of the sand. Flow rate is also affected by the length of the sand

column, as well as by the properties of the fluid (viscosity, density and raw water quality) and the sand

characteristics. For example, colder water should result in a slower flow rate, and over time, higher

turbidity raw water can affect flow rate by clogging the sand pores in the top centimeters of sand. In the

same way, porosity and specific yield, which are both dependent on the type of sand in the filter, can both

affect the hydraulic conductivity that is, how much water passes through an area of sand in a particular

time. Increasing the surface area or hydraulic loading, improving the raw water quality prior to filtration,


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using a filter in the tropics as opposed to cold climates, decreasing the sand height or changing the sand

type to coarser sand can all result in a higher flow rate.(Brett Gresham,1996)

2.9.1Effect of flow rates on bacteriological quality turbidity and colour removal

within a range, however, flow rates do not seem to affect bacteriological effluent quality. Traditionally,

flow rates in slow sand filters should be around 0.1 m/hour. Note that this is a compaction of m3/m

2/hour

and sometimes the unit is in days and not hours.

Flow rates can be increased up to 0.4 m/hour. Huisman and Wood (1974) reported the use of higher

filtration rates in the Netherlands (0.25 and 0.45m/hr) without any marked difference in effluent quality.

Also research done in India for continually operated sand filters found no significant difference in faecal

coliform reductions with flow rates of 0.1, 0.2 and 0.3m/hour (NEERI, 1982). However, it is possible to

increase the filtration rate considerably if effective pretreatment is given and if an effective disinfection

stage follows the filtration (Ellis, 1987).

Although the bacteriological quality of filtrate water does not deteriorate significantly with the filtration

rates higher than the conventional figure, turbidity and colour removal efficiency decline considerably

with higher filtration rates, although the filtrate quality remains reasonably good. Filtration rates higher

than the conventional one can therefore be adapted in slow sand filters if using a good quality of raw

water (Muhammad et al, 1996).

Lower flow rates are generally preferable. This is because of the following reasons:

A slower flow allows an increased pathogen removal, which is especially important in colder

climates where biological activity is more time-dependent (Huisman and Wood, 1974).

Depth of bacteria

with higher flow rates, bacteria will be found at deeper depths as their food supply is carried

deeper (Huisman and Wood, 1974) and so to ensure water quality, sand bed depth would need to

be increased. Lower flow rates are preferable to keep the bed depth within reasonable limits.

Breakthroughs

Lower flow rates that result from lower hydraulic loadings also ensure that other pathogens (such

as Cryptosporidium oocysts) are not pushed through to deeper depths, and that organic matter

does not break through.

Biofilm development

Lower flow rates may allow biofilms to become better developed.


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Slow sand filter designs should therefore incorporate an acceptable combination of hydraulic loading,

sand size, sand height and sand area for effective pathogen removal with a range of raw water qualities.

2.10 DARCY'S LAW

In 1856, Darcy published a simple relationship between the discharge velocity (v) and hydraulic gradient

(i) for flow through soil, which can be expressed as:

V=Ki

Where k = coefficient of permeability of soil (Wikipedia). The preceding relationship holds good for the

laminar flow of water through the void spaces in soil (sand and clay) and has been subjected to extensive

verification during the last 136 years. It was based on the results of experiments on the flow of water

through beds of sand. Based on these studies, it has been concluded that, for flow of water through fine

and medium sand, silt, and clay, the flow is laminar and Darcy's law is valid (International Journal 1992).

Laminar flow is one in which paths taken by the individual particle do not cross one another and moves

along well defined paths (R.K Rajput, 1998). Any flow with a Reynolds number (based on a pore size

length scale) less than one is clearly laminar, and it would be valid to apply Darcy's law. Experimental

tests have shown that flow regimes with values of Reynolds number up to 10 may still be Darcian.

Reynolds number (a dimensionless parameter) for porous media flow is typically expressed as

v d30/

where is the density of the fluid (units of mass per volume), v is the specific discharge (not the pore

velocity with units of length per time), d30is a representative grain diameter for the porous medium

(often taken as the 30% passing size from a grain size analysis using sieves), and is the dynamic

viscosity of the fluid.(Wikipedia).

From Darcys experiment velocity of a fluid through a porous media varies linearly with the loss of head

hf.

Consider a circular pipe of lengthLand diameterDcompletely filled with porous material of grain

diameterds.The flow takes place through the interstices of the porous material. If porosity isn,the

diameter of the passage through the particle isnds.The head loss through porous medium is

.10.31 Where hf = headloss in lengthL


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K= coefficient of permeability (depends on shape of passage)

= dynamic viscosity of fluid

w = weight density of fluid

u = average velocity of flow

D = characteristic length representing geometry of passage

Diameter of passage through particle is given by

d =nds

Substituting value of D with d in equation (10.31)

u= wn2ds

2 u/K*(hf/L) Or

Or V=Ki (Rajput 1998)

hf = KuL/wD2

hf = KuL/wn2ds

2

u= whfn2d2/K


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Assumptions

Darcy's law is a simple mathematical statement which neatly summarizes several familiar properties that

groundwater flowing in aquifers exhibits, including:

if there is no pressure gradient over a distance, no flow occurs (this is hydrostatic conditions),

if there is a pressure gradient, flow will occur from high pressure towards low pressure (opposite

the direction of increasing gradienthence the negative sign in Darcy's law),

the greater the pressure gradient (through the same formation material), the greater the discharge

rate, and

The discharge rate of fluid will often be different through different formation materials (or

even through the same material, in a different direction) even if the same pressure gradient

exists in both cases.

2.11. BIOSAND FILTERS

2.11.1 Biosand technologies

Biosand filters are a small, household sized adaptation of slow sand filters such that they can be

run intermittently. The filter consists of a layer of gravel overlain with prepared sand media

contained within a filter body or box, usually constructed on concrete. A shallow layer of water

sits at the top of the sand, where a biofilm (schmutzdecke) is created that further filters the water

of harmful microorganisms.

Operating the filter is very simple:

remove the lid, pour a bucket of water

into the filter, and immediately collect the

treated water in a clean container. This

filter was by Invented by David Manz,

PhD. University of Calgary.Household

biosand filters typically provide 30 liters

of water per hour, which is sufficient for a

family of five. Flow rate may decrease

over time as the filter becomes clogged,

but can be restored with cleaning. (Low-

cost water treatment technologies for

Figure 2.11.1: Biosand filter


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developing countries, 2010)

2.11.2 Contaminant Removal

Biosand filters have been shown to remove more than 90 percent of fecal coliform, 100 percent of

protozoa and helminthes, 95 to 99 percent of zinc, copper, cadmium, and lead, and all suspendedsediments. Biosand filters have also been shown to remove 76 to 91 percent of arsenic, reducing

it to acceptable concentrations. These filters do not sufficiently remove dissolved compounds

such as salt and fluoride or organic chemicals such as pesticides and fertilizers. The biological

layers effectiveness is influenced by temperature. Ammonia oxidation stops below 6 Celsius

and alternative treatment methods are required below 2 Celsius. Additionally, because biosand

filters are not able to handle high turbidity, they may become clogged and ineffective during

monsoon or rainy seasons.

Biosand filters require daily fillings during the 2 to 3 weeks when the biological layer is growing.Biosand filters also require regular cleaning, which involves agitating the water above the

biological layer. The filter will require 2 to 3 weeks of

nonuse after agitation to allow for the regrowth of the

biological layer. On occasion, the sand in the filter

needs to be cleaned as well. There are several

different methods to clean the sand, though all of them

require significant labor, significant training, or high

cost. User error has also been found to affect thefilters efficiency, especially because of the required 2

to 3 week nonuse period for growing the biological

layer. Biosand filters can be fabricated locally in

almost all regions because they use common

materials. (Low-cost water treatment technologies for

developing countries, 2010)

Figure 2.11.2: use of biosand filter


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2.11.3 Benefits & Drawbacks

Advantages

Removal of turbidity, color, odour

Good microbial removal

High flow rate

Can be constructed of local materials

Income generation

Durable

Minimal maintenance

Drawbacks

Not 100% microbial removal, may require post-disinfection

Limited transportation due to weight

Turbidity should not exceed 50 NTU (Low-cost water treatment technologies for developing

countries, 2010)

2.11.4 Biosand filters in Congo

Biosand filters purify dirty water so that it becomes safe to drink. They are very useful, both in rural and

urban areas which lack safe piped water. In Uvira, Democratic Republic of Congo, Tear fund has

introduced biosand filters in two areas of the city where water-borne diseases, such as cholera, are a

serious problem. Their objective is to encourage sustainability by providing the filters for sale, after first

ensuring local people are aware of the benefits of the filters so they will want to buy them. A social

enterprise, Bush Proof, trained technicians in the production and use of the filters.

2.11.4 The impact of biosand filters

These filters are really appreciated by the people in Uvira. They provide safe drinking water in a simple

way. When correctly used they help to control nearly all water-borne diseases such as diarrhoea, cholera

and typhoid. So far, 100 households in Uvira have bought, and are using, the filters after training.

Tests show that around 99% of microbes and contaminants are removed. The filter holds 20 litres of

water. After filling the filter, water will need to be collected in a clean jerry can.

Normally one litre of water is filtered every minute, so it will take 20 minutes for the contents of a 20 litre

bucket to pass through the filter. The filter can be used as often as needed. (E biosand.pdf)


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3

3.0RESEARCH METHODOLOGY

3.1EXPERIMENTAL SET UP

S1

S2

G1

T1

S3

T2

WATER TREATMENTWATER TREATMENTWATER TREATMENTWATER TREATMENT

Water to ta

E

C D

B

A

1

2

3

4


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A Water tank D bottle 2 T1, T2- Taps

B Filtering column E solar reflector G1- Gate valve 1

C Bottle 1 shows direction of water flow

S1, S2, S3- Sampling points

1- Pre filtering sand. 3- Sand

2- Pumice 4- Quarry dust

3.1.1 Column unit

The study was carried out using a fabricated plastic column at structures (ELA) building compound in

JKUAT.

3.1.2. Column set up and media packing

Figure 3.1.2 a fabricated filter column outside structures lab, JKUAT.


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The column was made of a black 4diameter PVC pipe, 2.65m in length. The column unit was adopted

based on observations from filter models designed and developed by SERVE for low cost household use

(Brett Gresham,1996).

The set up was as shown in figure 3.1.2. The water source for the set up was a plastic container of 20

litres placed above the column. The column unit had three strainers; two between the filter media and one

at the base. This was to prevent the media from washing out of position during operation.

Packing of filter media in the column unit was accomplished by gently pouring each medium in place into

the PVC pipe. Upon pouring in the media, the column unit was lightly tapped on the sides and the base to

facilitate close packing of the media; this was repeated until the level of each media was achieved. A

strainer was then inserted in place to hold the media in position. Warm water was then passed through the

media in order to minimize possibilities of air locks or entrapment that may interfere with effectiveness of

the filtration process. Water was allowed to settle for 24 hours in the plastic source before being released

into the column unit. The columns inlet water flow rate was controlled by adjusting the opening of the

gate valve below the plastic water source to minimize overflow. A constant flow rate was maintained by

having an assistant continuously pour water into the plastic source ensuring the water level doesnt go

below the initial level.

Inside the plastic source, pipe through which water flowed into the column was perforated. The

perforated holes were covered with a cloth and approx 4cm from the bottom of the plastic source. This

was to minimize the solids passing through the pipe into the column unit. A pre-filter was placed on top

of the column to remove any remaining solid particles in the water. This was a funnel filled with sand of

sieve size 1.2mm and a plastic strainer the bottom to allow the water, but not the sand, to pass. The sand

from this filter can easily be removed and washed, protecting the larger filter. The column unit contained

three layers of the filtering media of depth: 58cm quarry dust, 55cm sand and 1.5m pumice and were

arranged as in the set up model. The sieve sizes were: quarry dust (0.35mm) sand (0.40mm), pumice

(0.45mm).

These depths and sieve sizes were derived from the calculations below using Darcys law of filtration.

The water was filtered through pumice, sand and quarry dust at a filtration rate of 0.3m/hr. This was

derived from previous research.Huisman and Wood (1974) reported the use of higher filtration rates in

the Netherlands (0.25 and 0.45m/hr) without any marked difference in effluent quality. Research done in

India for continually operated sand filters found no significant difference in faecal coliform reductions

with flow rates of 0.1, 0.2 and 0.3m/hour (NEERI, 1982). It is possible to increase the filtration rate

considerably if effective pretreatment is given and if an effective disinfection stage follows the filtration


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(Ellis, 1987). The materials were arranged based on particle size with the largest particle size at the

bottom.

A sample filtrate was collected from tap T1 and tested in the JKUAT environmental laboratory. Tap T1

was also used to control the flow rate of filtrate into the bottles by regulating its opening. The filtrate

flowed through the adjacent pipe into the transparent bottles 1 and 2 where it was retained for2, 4 and 6

hours. The bottles were placed on a wooden reflector covered

with aluminum foil. This was to reflect more sunlight on the

bottles. From the bottles the water flowed through tap T2.

3.2 SIEVE ANALYSIS PROCEDURE

A sun dried sample of sand, quarry dust and pumice was

collected.

Pumice was crushed using a metallic bar to small pieces

so as to get the required size.

Stacks of clean sieves were prepared for each medium

with sieves having larger opening sizes placed above the

ones having smaller opening sizes.

The media was poured into the respective stack of sieves from the top and shaken.

The mass retained in the respective sieves was used as a filter medium. For sand, sieve of sizes

0.42and 0.59 were used, for pumice sieve of sizes 0.60 and 1.20mm and for quarry dust sieve of

sizes 0.42 and 0.30 were used. The mass retained in sieve size 0.30, 0.42 and 0.60 for quarry dust,

Sand and pumice respectively were used as filter medium.

3.3 SAMPLING PROCEDURES

3.3.1Sampling

A total of 14 samples were collected from wells and the properties

observed on each sample collected. The biological and chemical

analyses were carried out at Environmental and food science

Laboratories, JKUAT. The properties and methods of analysis are

presented in Table 3.5.

3.3.2Handling and treatment of sample

Figure 3.2: Mike sieving sand

Figure 3.3: collecting a sample from a

well


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The samples were taken to the environmental lab, JKUAT and tested on the same day for five weeks.

The sample with the highest level of pollutant(s) and the source

(well) were identified. The water from this well was filtered

through the filtering column.

3.4 LABORATORY TESTS

Data for the study were generated from primary source-

laboratory analysis. Sampling for groundwater involved three

basic steps; physical, chemical and biological properties.

Based on the guidelines by WHO (1996), the physical properties

examined included: color, turbidity, total dissolved solids, Ph.

Chemical properties were COD,BOD, ammonia and nitrite

while the biological property wasEscherichia coli.

3.5 DATA ANALYSIS

The data collected in the laboratory was analyzed using

excel.

The efficiency of filtering column(S1-S2) * 100= % pollutant removal

S1

The efficiency of sunlight treatment

(S2-S3) * 100 =% pollutant removal

S2

Figure 3.4: lab test of a sample

3.5:

/

.

S1Influent of filtering column

S2-Effluent of filtering column/influent of

bottle 1

S3-effluent of bottle 2


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3.6 DESIGN OF THE COLUMN UNIT

REF CALCULATIONS OUTPUT

Huisman et

al(1974) Filtration rate = 0.45 m/hr

For sand,

K = 1.0668 m/day, porosity, n = 0.25

ds= 0.4mm

L = whfn2ds

2/Ku

L = (9810*0.252*0.402*24*10000*0.1) L = 0.55m

(10002*1.0668*8.90*0.45)

For pumice,

K = 4.012m/day , porosity,n = 0.715

ds = 0.45mm

L = (10000*24*9810*0.1*0.7152*0.45

2)

(10002*(4.012)*8.90*0.45) L = 1.5m

For quarry dust

K = 4.5m/day , porosity, n = 0.60

Ds = 0.35mm

L= (9810*24*10000*0.1*0.62*0.35

2) L = 0.58m


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(10002* 4.5*8.90*0.45)

4

4.0 EXPERIMENTAL RESULTS AND DISCUSSION

4.1 RESULTS

INTRODUCTION

This chapter reviews the results of the data collected from the wells, performance of the column and

performance of sunlight treatment.

4.1.1 Water Quality in wells

Table 4.1.1 shows the values obtained in Wells in Juja.

Table 4.1.1: Results of the data collected from Juja wells

SAMPLE PH

BOD

(mg/l)

COD

(mg/l)

TSS

(mg/l)

E Coli

(cfu/ml)

TDS

(mg/l)

NH4

(mg/l)

TURBIDITY

(NTU)

COLOR

(mg/pt/l)

NO2

(mg/lN)

1 6.5 28 24 15 21 88 0 13.2 25 0

2 6.8 28 26 25 17 238 0 9.1 33 0

3 6.8 27 26 11 0 23 0 7.8 17 0.018

4 6.9 29 26 21 0 214 0 23.4 40 0.009

5 6.5 28 26 15 67 313 0.05 11.9 45 0.009

6 7.2 27 25 27 59 607 0 39.3 46 0.027

7 6.8 28 24 30 322 208 0 27.0 38 0.025

8 6.8 26 25 140 450 67 0 27.3 27 0

9 6.7 28 26 352 7.70E+03 1874 0 90.5 90 0.032

10 6.6 27 27 176 60 1629 0 22.8 50 0.046

11 6.5 28 26 158 580 256 0 39.4 45 0

12 6.7 29 26 28 467 132 0 19.0 42 0


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i. pH: The results of the analysis indicate that the pH values range between 6.5 and 7.2. This shows that

the values are within the desirable limits by WHO standards.

ii. Nitrite: Nitrite recorded low values in all wells. The results obtained in the analysis indicate that nitrite

is within the desirable limits set by WHO and Kenyan standards with range of values between 0.00 and

0.032 mg/LN.

iii.E. coli: The results of the analysis indicate thatE. coli was absent in 2(wells 3 & 4) of the 14 wells

and present in the other 12 wells. The values ranged between 0 cfu/ml and 7.7*103cfu/ ml. However, the

Kenyan and WHO standards suggest thatE. coli must not be detected in drinking water. Wells 1-9, 11-14

were located at residential areas. The areas had the presence of latrines (pit toilets), sewer pond and

garbage. Well 10 was located beside a road. Therefore the presence of these sanitation units could be said

to have direct impact on the groundwater of the study area.

iv. Total Dissolved Solids: - The results of the analysis indicated that 2 of the wells (well 9 & 10) had

values above the desirable limits set by WHO standards (


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4.2 Water quality after filtration

4.2.1 Filtrate from column unit (tap 1)

Results are in table 4.2.1.

i. pH: The results of the analysis indicate that the pH values range between 6.4 and 6.5. This shows that

the values are within the desirable limits by WHO standards and were not affected by filtration.

ii. Nitrite: There was a decrease in nitrite concentration from 0.0032 to 0.030 mg/l. This represented a

6.25 % change.

iii.E. coli: The results of the analysis indicate thatE. coli was reduced to 3364.9 cfu/ml from 7700

cfu/ml. This represented a 56.3 % removal of E coli.

iv. Total Dissolved Solids: - The results of the analysis indicated that the value was reduced to 560.326

mg/l from 1874mg/l. This represents 70.10 % reduction. This is below the limits set by WHO standards

(


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x.COD:-The results indicate a value of 24 mg/l.

4.2.2 Filtrate after sunlight treatment (tap 2)

Results are tabulated in table 4.2.2

i. pH: The results of the analysis indicate that the pH values range between 6.4 and 6.5. This shows a

slight increase in acidity although the values are within the desirable limits by WHO standards.

ii. Nitrite: Nitrite recorded a decrease of 20 percent in its value after Sunlight treatment.

iii.E. coli: The results of the analysis indicate thatE. coli was finally reduced to1016.1 cfu/ml after six

hours. This represented a 69.8 % removal of E coli.

iv. Total Dissolved Solids: - The results of the analysis indicated that the value decreased from 560.326

mg/l to 505.224 mg/l after 6h treatment. This represents 9.83 % reduction.

v. Total suspended Solids: - The results of the analysis indicated that the value was 28.340 mg/l .This

represented 18.7 % removal.

vi. Turbidity: - The results of the analysis indicated that the value decreased to 21.7 NTU. This

represents 33.35 % reduction in turbidity.

vii. Ammonia: - The results obtained in the analysis indicate the absence of Ammonia.

viii. Color:-The results indicate a reduction in color to 25 mg/pt/l.

ix. BOD: -The results indicate no change.

x. COD: - The results indicate no change.

/

/

/

/

/

4/

//

2/

2 4 6 28.2311 6.4 26 24 30.022 2823.5 2711.0 1317.4 28.101 0 1.5 27 0.028

2 6.5 25 24 2.384 2717.5 137.8 1134. 27.011 0 20.1 25 0.025

3 6.5 26 24 28.340 2016.6 1183.4 1016.1 27.262 0 21.7 25 0.024

4.2.2 ( 2).


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4.3GRAPHS


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4.4 DISCUSSION

a)

PH

Filtration of the water did not affect the acidity or basicity of the water. Adsorption is a physical process

and the impurities removed had no effect on the PH of water. However, after treatment with sunlight the

PH decreased. This means that the acidity of the water increased. This can be attributed to the nitrite in

the water. Nitrite dissolves in water to form nitric acid. The heat from the sunlight may have catalyzed the

process by increasing the water temperature. This acid may have raised the water acidity on dissolving.

However, the values were within the WHO limits.

b) Nitrite

Nitrite is a chemical element found in nitrogenous compounds e.g. fertilizers, urea, decaying plant or

animal matter etc. Nitrite concentration in this water was low and may be attributed to the fertilizers used

by the local residents in their small gardens, decaying plant/animal waste and the surrounding pit latrines.

During the rainy periods, percolating water leaches the nitrite to ground water. There was a slight

decrease in nitrite concentration after filtration and significant decrease after sunlight treatment.

Experiment results demonstrate no adsorption or dilution of NO2concentrations during filtration

(Julie Corriveau et al).The decrease may be due to nitrite dissolving into the water to form nitric acid.

However the value was still below the WHO limits.

c)

E. coli

The presence ofE. coli in drinking water indicates faecal contamination.E. coli strains cause intestinal

disease by a variety of mechanisms. Infections may resemble cholera, dysentery or gastroenteritis due to

salmonellae. There was a significant removal of E.coli by the filtering column. During the first run the

percentage change was minimal. This was because the column initially contained no bacteria and those

that were in the water attached themselves to the filter media while the rest passed through. On


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consequent runs the removal improved. A smaller size of sand will have a larger total surface area

available for biofilms to grow on, and therefore more biofilm can come into contact with the raw water.

The biofilms feed on the E. coli they come into contact with. This therefore improves treatment

effectiveness during filtration (Buzunis, 1995). Indeed, a greater combined surface area speeds up

chemical reactions (surface catalysis) (Huisman and Wood, 1974). A study by Logan et al (2001) into

Cryptosporidium oocyst removal suggested that the higher flow rates observed in coarser sand lead to

poorer bacteriological filtration. This poorer filtration occurs because there is less contact time for

biological predation on potential pathogens by the biological layer before the water passes through. In

addition, flow rates may cause thinner and sparser biofilms attached to sand grains. The size of the media

used was not convenient for slow sand filtration. This explains the low percentage removal of 56.3.

Moreover the E coli were not eliminated by sunlight. Solar water disinfection is a simple way to kill

bacteria in water. But the method requires strong sunlight and can only treat limited volumes of water. If

the bacteria are not completely inactivated by the sunlight, the dark periods give them time to recover

from the radiation damage, making them more resistant when reilluminated. (Solar power kills bacteria in

water).Particles causing turbidity reflected most of the light rays and thus reduced effective illumination

on E coli and thus not all could be killed.

d) Total dissolved solids(TDS)

An overall of 78.04% of the total dissolved solids were removed by the set up as a result of adsorption

and filtration. Adsorption is the adhesion of molecules of gas, liquid, or dissolved solids to a surface. This

process creates a film of the adsorbate (the molecules or atoms being accumulated) on the surface of the

adsorbent (Wikipedia).Some of the dissolved solids settled down in the source tank, others were trapped

in the pre-filter above the PVC column and the rest trapped in the PVC column unit. This percentage

would have been higher if lesser media size were used. The pore sizes of the used media were larger than

most of the dissolved particles thus allowing them to pass through. During sunlight treatment, percentage

reduction in TDS was very low. This was because there were no strainers to filter the water. The

reduction was due to settlement of the solids to the bottom during the six (6) hour treatment period.

However the level was reduced to allowable WHO limits.

e) Total suspended solids(TSS)

Suspended solids are those solids that remain floating on the water even after a considerable length of

time. The filtering column effectively removed most of the suspended solids from the water. This was as

a result of absorption and straining. The perforated holes on the pipe in the source tank and the sand in the

pre-filter filtered trapped additional suspended solids. However some of the suspended solids were

smaller in size compared to the media pores and the perforated holes thus passing through. The small


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change after sunlight treatment was due to lack of a strainer to trap additional suspended solids. Some

suspended solids settled after some time while the rest remained trapped in the bottles.

f) Color

Total dissolved solids result to a cloudiness of water. At sampling point 1(S1)

the color of the water improved significantly due to the large concentration

reduction of the total dissolved and suspended solids in the water as a result of

filtration and settlement. At sampling point 2(S2), the color improved because

some of the dissolved solids settled down.

4.5 Efficiency of the set up

In this project three properties (TDS, TSS andE. coli) were observed to be effectively removed by the set

up. Their overall efficiency was high (73.04 %, 91.95 %, 86.8 % respectively) compared to the other

elements. The highest % efficiency of the column was 91.95(E coli) and the lowest was 25(nitrite).The set

ups efficiency was poor in removal of turbidity and the level could not be lowered to allowable WHO

limits. This consequently affected removal efficiency of E.Coli. The average efficiency of the set up was

54.98 percent. The results are recorded in table 4.4 below. The low efficiency may be attributed to the

large media size and the infiltration rate. The large pores allowed a lot of solids to pass through. The

infiltration rate may not have allowed enough contact time for the sample and the filtering media.

Figure 4.4: filtered and

unfiltered samples


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4.4 .

%

%

() 0.5 32.56 64.02 32.56 21.7 33.35 5 76.02(/) 1874.000 560.326 70.10 560.326 505.224 .83 1500 73.04

(/) 352.011 34.85 0.10 34.85 28.340 18.7 30 1.5

.(/) 7700 3364. 56.3 3364. 1016.2 6.80 86.80

(//) 0 30 66.67 30 25 16.67 15 72.22

2(/) 0.032 0.030 6.25 0.030 0.024 20.00 3 25.00

4(/) 0 0 0 0 0 0 0.5 0

(/) 26 24 7.6 24 24 0 7.6

(/) 28 26 7.14 26 26 0 7.14


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5

5.0 CONCLUSION

Based on the findings of the study, it could be ascertained that there is evidence of both chemical and

biological pollution in the wells. The efficiency of the set up was good in the removal of turbidity, E coli

and total dissolved solids. The media are very poor in removal of nitrite and color; and effective in

removal of TSS. This set up is not favorable for treating very turbid water because of its low removal

efficiency. Sunlight can be effective in killing bacteriological pollutants but poor in removal of chemical

and physical pollutants. However, its effectiveness is affected by physical elements i.e TDS, turbidity and

TSS.

The sand, pumice, quarry dust and sunlight can be effective in well water purification.

5.1 RECOMMENDATIONS

There is need to determine efficiency of the individual medium. i.e quarry dust and pumice.

The use of this set up in removal of chemical pollutants should be further investigated.

Exposure of filtered sample to sunlight can be increased beyond 6 hours to determine whether

there is further improvement.


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6

6.0REFERENCES

AN INTEGRATED WATER, SANITATION AND HEALTH STRATEGY FOR THE

MUNICIPALITY OF RUIRU, KENYA School of International and Public Affairs (SIPA),

Columbia University, New York, NY. May 2007

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http/enwikipedia.org/wiki/anthropogenic

Biochemical oxygen demand Retrieved on 16/3/10 from

http://en.wikipedia.org/wiki/Biochemical_oxygen_demand

Brett Gresham(1996).The household slow sand filter .Retrieved 5 Nov 2009 from ///D:/project-

filtration/The household slow sand filter.htm

Burhanettin Farizoglu, Alper Nuhoglu, Ergun Yildiz and Bulent Keskinler Environmental

Engineering Department, Engineering Faculty, Ataturk University, 25240, Erzurum, Turkey.

Retrieved 26 October 2009 from http:// www.sciencedirect.com/science/

Chemical oxygen demand. Retrieved on 16/3/10 from

http://en.wikipedia.org/wiki/Chemical_oxygen_demand

Colour test. Retrieved on 10/3/10 from

http://www.tpub.com/content/construction/14265/css/14265_274.htm

Julie Corriveau, Eric van Bochove, Genevive Bgin and Daniel Cluis.Effect of Preservation

Techniques on the Determination of Nitrite in Freshwater Samples. Retrieved 5/3/2010 from

http://springerlink.com

Ellis, K.V. (1987). 'Slow Sand Filtration', WEDC J.Developing World Water, Vol 2, pp 196-198.

Estates department (2009) JKUAT BOX 62000 -00200 NAIROBI

Flue and chimney. The natural properties of pumice. Retrieved 02 November 2009

Gleick, P.H. (2002). Dirty Water: Estimated Deaths from Water-Related Diseases 2000-2020.

Pacific Institute.

'Global Water Supply and Sanitation Assessment 2000 Report', section 2.2, WHO 2000

retrieved02 NOV 2009 from http://www.lenntech.com/library/diseases/diseases/waterborne-

diseases.htm

Heartfelt pharmacy, Juja.Data collected November 2009.


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Huisman, L; Wood, W.E. (1974). Slow Sand Filtration. WHO, Geneva, Switzerland. p.44.

Available from IRC

International Journal of Offshore and Polar EngineeringVol. 2. No.4. December 1992 (ISSN

1053-5381) Hydraulic Conductivity of Loose Coarsesand by R.M. Smith, B.M. Das*, V.K.

Puri*, S.C. Yen* and E.E. Cook*Department of Civil Engineering and Mechanics Southern

Illinois University at Carbondale, Illinois, USA.

Journal of sedimentary research, September 1984 vol54 no.3 pg899-907.

Logan, A.J.; Stevik, T.K.; Siegrist, R.L.; Rnn, R.N. (2001). Transport and fate of

Cryptosporidium parvum oocysts in intermittent sand filters. Water Resource. Vol. 35, No. 18,

pp.4359-4369.

Low-cost water treatment technologies for developing countries.Retrieved on 13 January 2010

from www.jalmandir.com/biosand/

Muhammad, N.; Ellis, K.; Parr, J.; Smith, M.D (1996). Optimization of slow sand filtration.

Reaching the unreached: challenges for the 21st century. 22nd WEDC Conference New Delhi,

India, 1996. pp.283-5. Retrieved 03 November 2009 from http://wedc.lboro.ac.uk

National Environmental Engineering Research Institute (NEERI). (1982) Slow sand filtration.

Final project report, Nagpur, India.

R.K.Rajput (1998).Laminar flow A TEXT BOOK OF FLUID MECHANICS AND

HYDRAULIC MACHINES in SI units.1stedition pp 194,572-3.

Schulz, C.R.; Okun, D.A. (1984). Surface water Treatment for Communities in Developing

Countries. IT, London. p.193. Retrieved 18 October2009 from www.developmentbookshop.com

Solar power kills bacteria in water .Retrieved 24/2/10 from

http://www.rsc.org/Publishing/Journals/PP/article.asp?doi=b816593a

The eruption of Soufriere hills volcano Montserrat (1995) by Timothy H Druitt and B Peter

Kokelaar. Pg157.

Total dissolved solids. Retrieved on 16/3/10 from

http://en.wikipedia.org/wiki/Total_dissolved_solids

Total suspended solids. Retrieved on 16/3/10 from

http://www.adbio.com/science/analysis/tss.htm

Turbidity-wikipedia.Retrieved on 24/2/2010 from http://en.wikipedia.org/wiki/turbidity

University of Nairobi (UON) Urban Planning Studio 2005.

Water colour .Retrieved on 5/3/10 from http://en.wikipedia.org/wiki/Color_of_water


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WATER POLLUTION from wiki encyclopedia retrieved 26 October 2009 from

http/enwikipedia.org/wiki/water_pollution/

Water testing 101:TDS Retrieved on 16/3/10 from http://www.wqpmag.com/Water-Testing-101-

TDS-article8837

WHO (1996): Guidelines for Drinking Water Quality Vol.II. World Health Organization Geneva.

WHO (2000): Water for Health. World Water Day 2000, Washington.

Xiyu Li, Weihu Yang, Qin Zou, Yi Zuo. (2009) Tissue Engineering Part C: Methods. Retrieved

02 November 2009 from http://www.liebertonline.com/doi/abs/10.1089/ten.TEC.2009.0285

Yahoo (2009). What are the three properties of sand?

http://answers.yahoo.com/question/index?qid=20081218182613AAOZGd9

6.1 TABLES AND PLATES

WHO DRINKING WATER GUIDELINES


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1 :

2 :

3: ,

6:

4:

7:

8:


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Documents

Murithi M - Purification of Well Water in Juja