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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
ANTHROPOGENICfrom wiki encyclopedia. retrieved 02 November 2009 from
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
7/26/2019 Murithi M - Purification of Well Water in Juja
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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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