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PERPUSTAKAAN UMP
100 IH I0 I0 111 00 1111110 0000092417
RAINWATER HARVEII1Nu I 1tM ruic. LAINLRUAPE USE IN GAMBANG
CAMPUS, UNIVERSITI MALAYSIA PAHANG (UMP)
NUR ATILYA BINTI MAHIDAN
Thesis submitted in fulfillment of the requirements
for the award of the degree of
Bachelor of Civil Engineering
Faculty of Civil Engineering and Earth Resources
UNIVERSITI MALAYSIA PAHANG
JANUARY 2014
Vi
ABSTRACT
Rainwater harvesting system is the collection of rainwater mostly via rooftop and stored in cistern for potable and non potable use. The purpose of this study is to find out rainwater quality harvested from rooftop and to obtain a rainwater harvesting system for collecting natural water. This research only considers determination of rainwater storage tank size by estimating rainwater supply and landscape water needs. Qualitative'assessment of rainwater collected via rooftop was determined using two selected roofing materials namely galvanized iron roofing sheet and clay tiles roofing sheet. The samples were collected directly from downpipe and the quality of rainwater was determined using standard method in, laboratory. The test included chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (TSS), ammoniacal nitrogen, eseherichia coli E-Coli) :and total coliforni. The study water quality classified as Class IV compared with National Water Quality Standard (NWQS). It was found that rainwater from galvanized iron roofing sheet was more polluted, followed b y clay tiles roofing sheet, The rainwater also is suitable to use for landscape irrigation, due to the water quality classification. For landscape watering in KKI Student Park, 50m3 is the monthly maximum volume of water needed for irrigation.
VII
ABSTRAK
Sistem penuaian air hujan adalah merujuk kepada pengumpulan air hujan untuk kegunaan minuman dan bukan minuman. Kebiasaannya, air hujan dikumpul di dalam tangki setelah melalui permukaan bumbung atau dikumpul secara terus. Tujuan penyelidikan mi adalah untuk mengenalpasti kualiti air hujan dari lanian bumbung dan mernperoleh satu sistem penuaian air hujan untuk mengumpul air sernulajadi. Penyelidikan mi hanya rnenyentuh pengiraan tangki air hujan dengan mengira bekalan air hujan dan keperluan air untuk pengairan lanskap. Penilaian kualiti air hujan yang dikutip dari bumbung dibuat keatas dua jenis bumbung laltu bumbung jenis besi bergalvani dan jubin tanah hat Sampel air, hujan yang dikutip kemudiannya diujikaji di dalam maknial mengikut kaedah standard yang ditetapkan. Antara Ui Ian yang dibuat ialah chemical oxygen demand (COD), biochemical oxygen demand BOD), total suspended solids (TSS), ammoniacal nitrogen, eschenichia coli (E-CoIi) dan total coliform. Keputusan ujian kernudiannya dibandingkan dengan Kelas 4 Standard Kualiti Air Negara (NWQS). Daripada keputusan yang didapati, dapat disimpuikan bahawa kesemua air hujan mengandungi baktenia (E.Coii>1) kecuali dua sampel air hujan dari larian bumbung besi bergaivani. Didapati bahawa air larian hujan dan bumbung besi bergalvani Iebih tercemar berhanding air larian hujan dari bumbung berjubin tanah liat.Air hujan yang dikutip melalui bumbung juga sesuai untuk tujuan pengairan kerana semua niiai yang dikehendaki kurang daripada nilai rnaksirnum bagi Kelas 4. pengairan lanskap pula, didapati isipadu maksimum air hujan yang diperlukan untuk pengairan selama sebulan adalah 50m3.
VIII
TABLE OF CONTENTS
Page
SUPERVISOR'S DECLARATION Ii
STUDENT'S DECLARATION
ACKNOWLEDGEMENTS iv
ABSTRACTS v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF ABBREVIATIONS xiv
CHAPTER 1 INTRODUCTION
1.1 General Introduction 1
1.2 Problem Statement 2
1.3 Objectives 3
1.4 Scope of Study 3
1.5 Expected Outcome 3
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 4
2.3 Rainwater harvesting system 5 2.11 Common rainwater harvesting components 6 2.3.2 Rainwater harvesting for irrigation 8
2.4 Water quality of rainwater 9 2.4.1 Roofing sheet material 10 2.4.2 Storage material 11 2.4.3 Location 11, 2.4.4 Types of contaminants in rainwater tank systems 12
ix
CHAPTER 3 MATERIALS AND METHODS
3.1 introduction 14
3.2 Study area and sampling location 15 3.2.1 Study area and sampling location for water quality analysis 15 3.2.2 Study area for analysis of rainwater harvesting system 15
for landscape use
3.3 Testing of parameter 16
3.3.1 pH 17 3.3.2 Dissolved oxygen 17 3.3.3 Biological oxygen demand 18 3.3.4 Chemical oxygen demand 18 3.3.5 Total suspended solids 19 33.6 Escherichia Coil 19 3.3.7 Ammoniacal nitrogen 20
3.4 Obtain rainwater harvesting system for landscape use 20
3.4.1 Study area observation 20 3.4.2 Malaysia meteorological data 20
CHAPTER 4 RESULTS AND DISCUSSIONS
4.1 introduction 21 4.2 Water quality 21
4.2.1 pH 22 4.2.2 Dissolved oxygen • 23 4.23 Biological oxygen demand 23 4.2.4 Chemical oxygen demand 24 4.2.5 Ammoniacal nitrogen 25 4.2.6 Total suspended solids 26 4.2.7 Escherichia Coli 27 4.2.8 Total coilform 28 4.2.9 Summary of rooftop rainwater quality 29
4.3 Sizing the rainwater harvesting tank 30
4.11 Rainfall quantities 31 4.3.2 Rainfall pattern 32 4.3.3 Capacity of rainwater harvesting tank 33
x
4.3.4 Potential rainwater supply 34 4.3.5 Potential landscape demand • 36 4.3.6 Rainwater source reliability 41 4.3.7 Sizing storage tank for landscape irrigation needs 42 4.3.8 Automatic switching system 43 4.3.9 Cost saving 44
CHAPTER 5 CONCLUSION AND RECOMMENDATIONS
5.1 Conclusions 47
5.2 Recommendations 48
REFERENCES 49
APPENDICES 51
A interim National Water Quality Standard 51
B Monthly rainfall 52
C Relative humidity 53
D Global radiation 54
E Temperature 55
F Wind speed 56 G Result of water quality 57
A
LIST OF TABLES
Table No. Title Page
2.1 Types of contaminant commonly found in rainwater collection system 12
3.1 DO level and its associate water quality 17
4.1 Summary of rainwater quality from selected roofing materials with 29 Class IV NWQS
4.2 Runoff coefficients for selected catchment surface 34
4.3 Summary of potential rainwater supply from January 2013 to October 2013 36
4.4 Monthly reference evapotranspiration from Kuantan weather station 37 for year 2Ol3 -
4.5 Summary values for landscape coefficient factors 38
4.6 Summary values for landscape monthly water needs 39
4.7 Monthly landscape demand for January until October in year 2013 41
4.8 Supply and demand balance for the January 2013 to October 2013 for 42 RWHS in student park
4.9 Cylindrical PE storage tank for various height and diameters 43
XII
LIST OF FIGURES
Figure No. Tide Page
2.1 Rainwater harvesting category
2.2 Elements of rainwater harvesting system 6
2.3 First flush diverter 7
3.1 Research methodology flow 14
3.2 Location of sampling abd study area for water quality analysis 15
3.3 Location of study area of rainwater harvesting for landscape use analysis 16
4.1 Clay tiles and galvanized iron roofing sheet 21
4.2 Comparison of pH value of rainwater from different roofing materials 22 at various rainfall periods
4.3 Comparison of DO value of rainwater from different roofing materials 23 at various rainfall periods
4.4 Comparison of BOD value of rainwater from different roofing materials 24 at various rainfall periods
4.5 Comparison of COD value of rainwater from different roofing materials 25 at various rainfall periods
4.6 Comparison ofAmmoniacal Nitrogen value of rainwater from 26 different roofing materials at various rainfall periods
4.7 Comparison of Total Suspended Solids value of rainwater from 27 different roofing materials at various rainfall periods
4.8 Comparison of Escherichia Coli count of rainwater from different 28 roofing materials at various rainfall periods
4.9 Comparison of Total Coliform count of rainwater from different 29 roofing materials at various rainfall periods
4.10 Common rainwater harvesting component for landscape irrigation 30
4.11 Student park landscape area in KK1 30
XIII
4.12 Location of proposed rainwater tank next to C14 building 31
4.13 Monthly rainfall obtain from Kuantan weather station for year 2013 32
4.14 Number of consecutive dry and wet days obtained from Kuantan weather 33 station for year 2013
4.15 Rooftop area of C14 building considered as catchment surface 35
4.16 Landscape requirement and monthly rainfall 42
4.17 Automatic switching system for rainwater supply and potable water 44
4.18 Water tariff per rn3 of water in state of Pahang 45
LIST OF ABBREVIATIONS
APHA American Public Health Association
BOD Biochemical Oxygen Demand
CERRM centre for Earth Resources Research & Management
COD Chemical Oxygen Demand
DO Dissolved Oxygen
E-Coli Eseherichia Coli
ETo Reference Evapotranspiration
FAO-56PM FAO Penman-Monteith Paper No 56
JPS Jabatan Pengairan dan Saliran
Kc Landscape Coefficient
Kd Density Factor
KK1 Kóiej Kediarnan 1
Kmc Mcroclirnate Factor
Ks Species Factor
mg/L milligram per litre
mL millilitre
MMD Malaysian Meteorology Department
MPN Most Probable Number
NWQS National Water Quality Standard
PAIP Perbadanan Air Pahang
PE Polyethylene
TSS Total Suspended Solids
xiv
xv
Uv Ultra Violate
WUCOLS Water Use Classifications of Landscape Species
CHAPTER 1
INTRODUCTION
1.1 GENERAL INTRODUCTION
Water is essential to all life on earth- human, animal and vegetation. Increasing
population, expansion of urbanization, industrialization as well as agriculture imposed
the growing of demand and pressure on water resources. A new development of water
resources such as new water supply scheme results in rising costs and significant impact
to the environment. The developments of urban areas increase the imperviousness of
land, which affect or alters the hydrological processes. The potential problems include
an increase of total runoff volume, increase of peak runoff flow, decrease on time to
concentration, and deteriorated water quality (Dietz, 2007).
Rainwater harvesting (RHS) is an ancient practice that has been increasingly
receiving attention in the world, fuelled by water shortages from droughts, pollution and
population growth (Noide 2007; Meera and Ahameed 2006). Historically, harvested
rain water provided water for drinking, landscape watering, and for agricultural uses.
Recently, environmental concerns have increase the appeal of green building practices,
including rainwater harvesting systems, in urban areas. Rainwater harvesting is
especially appealing as it combines the benefits of water reuse with runoff reduction and
groundwater recharge. Additionally, rainwater is available free of charge and puts no
added strain on the municipal supply.
RHS is consisting of 4 components; catchment areas usually roof, conveyance
I
systems, storage and distribution systems to control where. the water goes. For
FA
conveyance systems, the gutter and downspouts direct the water from the catchment
area to the storage container. Gutters are either concealed inside the walls of buildings
or attached to the exterior of buildings. The purpose of storage is by making water
available when it is needed. Storage can be underground or above-ground. Storage
containers can be made of polyethylene, fibreglass, wood, or metal. The distribution
system can be a hose, constructed channels, pipes, or manual drip system that directs the
water from the storage containers to landscaped areas.
1.2 PROBLEM STATEMENT
Population growth is inevitable. In Malaysia, population has increased from 8.1
million in 1960 to 27 million in 2008. As the population increases, the water demand
from clean water increases as well. And to cater the demand, dams and water treatment
plant has to be constructed to meet the needs of the people. As the supply and demand
are in a eat and mouse race, with the limited water'resources, eventually the demand
will exceed the supply and this situation will create problems to the country.
The people's attitude also plays an important part towards creating a.sustainable
living. Campaigns had been going to educate and remind the public that water is
precious thus it is lot to be wasted. Not only will it save the water 'bill but also reduce
the water stress on water demand as well as possess sufficient reserves for emergencies
uses such as droughts and dry spells.
Since water is important, it is seen as a waste for it to be used for flushing toilets
and for watering plants. Furthermore, rainwater can be used as a substitute by collecting
and utilise it rather than let it go to waste. Besides, by using rainwater as an alternative,
clean water can be saved and be used for other purposes and simultaneously decrease
the demand of clean water which resulted in lower cost of water bill and cost of
operations in the water plants. The use of untreated rainwater for non-potable uses that
would otherwise be supplied by potable water ultimately conserves municipally
supplied potable water (Persyn, 2004).
3
1.3 OBJECTIVES
The study objectives are as follows:
i. To determine the quality of collected rainwater.
ii. To obtain a rainwater harvesting system (RHS) for collecting of natural water.
1.4 SCOPE OF STUDY
Once the rainwater falls on rooftop catchment, the quality can be doubted. Two
types of roofing materials will be considered for water quality assessment namely
galvanised iron and clay tiles roofing sheet. Several test need to be carried out using
standard method and classification of water quality will be based on Class IV National
Water Quality Standard (NWQS). The tests involved are Biochemical Oxygen Demand
Chemical Oxygen Demand, Total Suspended Solids, Ammoniacal Nitrogen,
Escherichia Coli and Total Coliform.
To obtain rainwater harvesting system for collecting of natural water, it was
necessary to obtain weather data from Kuantan weather station. Since the proposed
building for rainwater catchment already has gutter and downpipe installed, thus this
study only focused on estimating rainwater storage tank size. The catchment area which
is rooftop area of the building will be calculated based on the aerial map of the campus.
The potential rainwater harvesting volume is estimated based on the total rooftop area,
the monthly rainfall and the runoff coefficient. After that, volume of rainwater needed
by landscape plant is calculated based on evapotranspiration, landscape coefficient,
irrigation efficiency and total area of landscape.
1.5 EXPECTED OUTCOME
i. By testing the parameter, the quality of collected rainwater can be classified
based on National Water Quality Standard.
ii. With proper calculation and estimation, adequate storage tank to capture
rainwater for rainwater harvesting system can be obtained for landscape use in
KKI Student Park.
CHAPTER 2
LITERATURE REVIEW
2.1 INTRODUCTION
According to the Regent of Perak Raja Dr Nazrin Shah, the global competition
and even conflicts in water usage are likely to occur if proper water resource
management is not carried out immediately. The world's population was expected to
increase by 30% in 2005 and the pressure of fresh water for human consumption would
be more critical (The Star, 2008).. Malaysia is considered rich in water resources with an
annual average rainfall of about 3,000mm generating 556 billion m3 of surface runoff
and renewable water resources amounting to 120 billion m 3 per year (Salmah and
Rafidab, 1999). Even then, water supply disruption due to a tight water supply and
demand situation aggravated by a lack of rainfall over catchment areas coupled with
river pollution problems at the water intakes, do occur, as in the 1998 drought which
brought unpleasant water supply disruption for some 1.8 million Klang and Langat
Valley residents (Jarnai.luddjn and Adhityan, 2.007).
Rainwater harvesting and utilization has been practiced in Malaysia especially in
the villages since long ago. Subsequent to the 1998 April drought, the Minister of
Housing and Local Government on 7 May 1998 has expressed the Government's
interest for houses to be designed to include facilities for collecting rainwater. In 1999,
the Ministry of Housing and Local Government has produced a Guideline on Installing
a Rainwater Collection and Utilization System (Jamalluddin and Huang, 2007).
4
5
However, there are several factors that need to be put into consideration when
using rainwater harvesting system. One of the factors is harvested rainwater quality.
Initially, rainwater is free of microbial contamination, but it may become contaminated
by animals and humans or, alternatively, human pathogens may grow in stored
rainwater resulting in significant human health risk from infectious diseases (Schets,
Italiaander, van den Berg and De Roda Husman, 2010.) Although the water quality
requirement for non potable uses is low compare to potable use, assessment of water
quality need to be carried out in order to confirm the water will not caused harm to the
people skin.
2.2 RAINWATER HARVESTING SYSTEM
In scientific term, rainwater harvesting refers to the collection and storage of
rainwater and also other activities aimed at harvesting surface and groundwater,
prevention of looses through evaporation and seepage and all other hydrological studies
and engineering interventions, aimed at conservation and efficient utilization of the
limited water endowment of physiographic unit as a watershed (Agrawal and Narain,
1999). The category of rainwater harvesting is shown in Figure 2.1.
Dirict harvPstin o Amo.henc fc dw end snow water ren,, snow,
Rnocff Infiltration
Rnwater Saurcu Swlace watet reanurces GoundW.ter (River,. IMce. reservairt) (ve11,. pan bocebae,)
Sm$lacele Medum-sceiv araeac&e
F ROCt od 1 Water Lthwtsr Ienyertii Catthiiere Catdinsne Catthnwa storage rvetti
L syatwas syateno [ wans wthoam 9-OP -
Itoecwsnaiiption Rwff ru-eors end ,maaor ft"rac - - - wareeneat MtO
-,P* catsrent bumb, act GtO1eatir R.edtarp
Figure 2.1: Rainwater Harvesting Category
Source: Jamaliudin and Huang (2007)
6
2.2.1 Common Rainwater Harvesting Components
Ideal domestic rainwater-harvesting systems generally composed of six basic
components and these components are the roof (catchment), gutters and down pipes,
primary screening and first flush diverters, storage tanks, the pipes, and water treatment
unit.(TWDB, 1997). Figure 2.2 shows the elements of rainwater harvesting system.
Elements of rainwater Karvestmg Svstem
Catchment r and Pttraton Storage 1 Delivery Treatment su^rfwe
upout 1 Do Tank Ste Sy m Purification
4, I The
4,
Channel4 4
Also known4
Type of 1
4, _____
Io- Potablee Icollection water from 3Jj5f as cisterns delivery Pctahle Us surface the roof to MOM cystem Uses
from which the tank
rainfalldust frown the
factors at
I runoff rainwater before
the stcreae
to the tank Fed
Man Made Natural I Filtration Filtration Surface Surface I only and Budget Personal Disinfection
[ Preference
Rainwater iDemse7 Oy Ctthment Aesthetics Supply I Season Surfa
Figure 2.2: Elements of Rainwater Harvesting System
Source: Che Ani et al., (2009)
2.2.1.1 Catchment
The catchment of a water harvesting system is the surface which directly
receives the rainfall and provides water to the system. It can be a paved area like a
terrace or courtyard of a building, or an unpaved area like a lawn or open ground.
Rooftop rainwater harvesting comprised of the rooftop as the catchment area, connected gutters and pipes to a storage container. The most suitable rooftop surfaces are
corrugated iron sheets, tiles and asbestos sheets. Thatched roofs pose problems as the runoff is less and generally of a low quality (Yaziz, 1989). Other type of roof made of
reinforced cement concrete (RCC), galvanised iron or corrugated sheets can also be used for water harvesting.
7
2,2.1.2 Gutter and downspout
Gutter refers to channels all around the edge of a sloping roof to collect and
transport rainwater to the storage tank. Gutters can be semi-circular or rectangular. The
function of guttering is to protect the building by collecting the water running off the
roof and direct it via the downpipe to the storage tank. The gutter system should have a
uniform slope of 0.5% and be large enough to collect the heavy runoff from high
intensity rains (O'Brien, 1990).
2.2.1.3 First flush diverter
The purpose of first flush diverter is to remove contaminant before entering
storage tank. The first flush usually contains higher concentration contaminants than
rooftop runoff from later in the storm. . With all roof catchment tanks, the first 20 to
30L of rainwater running off the roof, which conitain large quantities of leaves and bird
droppings, should be discarded to keep the water potable (O'Brien, 1990). A common
first flush diverter is shown in figure 23. Water will not begin to flow into the storage
tank until the diverter has filled completely.
P49w'n5pout - from gutters
ee juncon- LbO%A/ E'aIi 5eat._-
ioatfrig I 5ealtng baiL (optionaL)
I I '\—To cistern -
ócrew cap
Figure 2.3: First flush diverter
Source: Waterfall (2004)
8
2.2,1.4 Storage system
Storage allows full use of excess rainfall by making water available when
needed. Before water is stored, it should be filtered to remove particles and debris.
Storage container can be located above ground or underground. Mostly it is made of
Polyethylene, fibreglass, wood, concrete or metal (Waterfall, 2004).
2.2.1.5 Distribution
The distribution system directs water from the storage container to landscape
areas. The distribution device can be a garden hose, constructed channels, pipes,
perforated pipes, manual drip system and sprinider system. A manual or electric valve
located near the bottom of the storage container can assist gravity-fed irrigation. In the
absence of gravity flow, an electric pump hooked to a garden hose can be used. A pump
will be required to provide enough pressure to operate a typical drip irrigation system
(Waterfall, 2004).
2.2.2 Rainwater Harvesting For Irrigation
It is important to estimate the volume of rainwater harvesting and also to know
the water consumption. The domestic water consumption is different from country to
country in the world (Mohammed et al., 2006).A rainwater harvesting system for
irrigation purposes has three components, namely the supply source from the catchment
surface area, the demand which is the landscape water requirements and the conveyance
system to moves the water to the plants (Waterfall, 2004).
The volume of rainwater planned to be used for irrigation is mainly depends on
rainfall intensity, rainfall duration, frequency of the rainfall, and degree of saturation for
catchment ground surface and its nature. Water harvesting cannot provide a completely
reliable source of irrigation water because it is dependent on the weather, and weather is
not dependable. Water used for irrigating plant of a landscape from a rainwater
harvesting system can be determined by two methods namely supply method or demand
method. (Mohammed et al., 2006).
9
2.2.3 Determination of Potential Rainwater Supply and Landscape Water Demand
According to Mohammed et al. (2006), the equation 2.1 can calculate potential
harvested rainwater from rooftop catchment.
S=AxCxR
(2.1)
Where S is monthly yield of rainwater harvest, A is catchment area, C is runoff
coefficient, and R is the monthly rainwater depth. Although in reality the amount of
water available fluctuates on a daily basis but for simplicity the computation can be
done on a monthly basis (Mohammed et al., 2006).
The volume of water required by the plants is computed based on monthly
evapotranspiration data using the following equation:
DEToxBxA
(2.2)
Where D is monthly water demand or volume of irrigation water, (ETo) is
monthly evapotranspiration, B is the plant factor, and A is the Irrigated area. Using
plants of similar water requirements will simplify the system and make the amount of
water needed to maintain those plants easier to compute. Both equations above are
usually used to compute yield and demand for both new and established landscapes. In
case that all the units of the variables used in m 2 and m then the unit of both supply and
demand will be in in2. The plant factor represents the percent of ETo that is needed by
the plant and it mainly depends on the type of the irrigated plant whether it's high,
medium, or low water use (Mohammed et al., 2006).
2.3 WATER QUALITY OF RAINWATER
The quality of water collected in a rainwater harvesting system is affected by
many factors, including;
o Environmental conditions such as proximity to heavy industry or major roads,
the presence of birds or rodents (Forst, 1998 and Taylor, 2000).
o Meteorological conditions such as temperature, antecedent dry periods, and
rainfall patterns ([vans, 2006).
10
• Contact with a catchment material and the dirt -and debris that are deposit upon it
between rainfall events (Simmons, 2001 and Van Metre an Mahler, 2003).
• Treatment by pre-cistern treatment devices such as filtration of first-flush
diversion (Yaziz, 1989 and Martinson & Thomas, 2005).
o Natural treatment processes taking place within the rainwater cistern (Scott and
Wailer, 1987 and Spinks, 2003)
o Treatments by post-cistern treatment devices such as particle filtration,
ultraviolet disinfection, chlorination, slow sand filtration or hot water systems
(Coombes 2000, Kim 2005, Ahameed and Meera 2006, Sazakli 2007).
The microbiological quality of stored rainwater may depend on storage
conditions such as temperature and time, but also on the materials of which the storage
container are made maintenance of the system and hygiene practice at the tap (WHO,
2006).
2.3.1 Roofing Sheet Material
Contamination from roof surfaces can come from two main sources. Particles
can accumulate on the roof surface either from direct atmospheric deposition, or from
overhanging foliage or bird and rodent debris (Despins, Farahbakhsh and Leidi, 2009).
From the study of Radaideh et al. (2009) found that harvested rainwater from rooftops
have better quality than water collected from the catchment areas.
Metal roofs are often associated with the leaching of trace elements, detected in
the dissolved form in the runoff itself and adsorb to the particulate matter washed from
the roof. Concentrations of dissolved and particulate copper from copper flashings are
increased compared with both pure rainwater and runoff collected from clay or concrete
tiles (Forster, 1996). The same situation also applied to zinc concentration in runoff
from a zinc sheet roof and, to a lesser degree, from zinc gutters. Van Metre and Mahler
(2003) compared galvanized metal roofs to be a greater source of both zinc and
cadmium contamination, while asphalt was associated with higher levels of lead and
Possible mercury. However, there is no significant difference between concentrations of
lead, zinc or copper in runoff from asphalt roofs and metal roofs (Hart and Wide, 2006).
ii
23.2 Storage Material
Rainwater is often slightly acidic, the increase in pH caused by contact with a
concrete tank is beneficial for the protection of the distribution system and the chemical
quality of the water by minimizing the potential for leaching materials (Despins,
Farahbakhsh and Leidi, 2009). According to Scoot and Walker (1987), in a study
evaluating the quality of stored water in a concrete cistern it is report that a rise in pH
from 5.0 on the roof surface, 9.4 in the tank and 10.3 from the tap. A higher pH can
inhibit colifomi growth.
Although it is generally considered as a quality enhancer, storage cisterns also
cause some concern over the potential for chemical leaching. Leaching of zinc from
metal tanks was found to be significantly in one study, but concrete or plastic tanks did
not have any notable impact on the concentration of zinc, lead or copper (Hart and
White, 2006).
2.3.3 Location
Depending on where the system is located, the quality of rainwater itself can
vary, reflecting exposure to air pollution caused by industries such as cement kilns,
gravel quarries, crop dusting, and a high concentration of automobile emissions
(Mohammed et al., 2006),In most industrialized urban areas, the atmosphere has often
been polluted to such a degree that the rainwater itself is considered unsafe to drink
(Thomas, 1993).Heavy metals such as lead are potential hazards especially in areas of
high traffic density or in the vicinity of heavy industries (Yaziz et al., 1989, and Thomas
et al., 1993). Organic chemicals such as organ chlorines and organophosphates used in
biocides can also contaminate rainwater. Although serious atmospheric contamination
of rainwater is normally limited to urban and industrial locations, studies in the north
eastern of United States revealing the presence of pesticides and herbicides in rainwater
do give some cause for concern (Richards et al., 1987). Despite the numerous sources of
atmospheric pollution, in most parts of the world, especially in rural and island
locations, levels of contamination of rainfall are low. Most contamination of rainwater
occurs after contact with the catchment surface (roof or ground) and during subsequent
delivery and storage (Wailer, 1989).
12
2.3.4 Types of contaminants in rainwater tank systems
From the study conducted by Mosley (2005), the types of contaminants
commonly found in rainwater collection systems are listed below. However the type of
contaminants may varies from places to places and depends on the design of rainwater
collection system as shown in the following tables:
Table 21: Types of contaminants commonly found in rainwater collection system
Contaminant
Dust and ash
Pathogenic bacteria
Heavy metals
Other inorganic
contaminants (e.g. salt
from seaspray)
Source
Surrounding dirt and
vegetation
Volcanic activity
Bird and other animal
droppings on roof, attached
to dust
Dust, particularly in urban
and industrialized areas,
roof materials
Seaspray, certain industrial
discharges to air, use of
unsuitable tank and/or roof
materials
Risk of entering rain
tank
Moderate : Can be
minimized by regular roof
and gutter maintenance
and use of a first-flush
device.
Moderate : Bacteria may
be attached to dust or in
animal droppings failing
on the roof. Can be
minimized by use of a
first-flush device and good
roof and tank maintenance.
Low: Unless downwind of
industrial activity such as a
metal smelter and/or
rainfall is very acidic (this
may occur in volcanic
islands).
Low: Unless very close to
the ocean or downwind of
large-scale industrial
activity
13
Table 2.1: Continued
Contaminant Source - Risk of entering rain
tank
Mosquito larvae Mosquito laying eggs in Moderate: If tank inlet is
guttering and/or in tank screened and there are no
gaps, risk can be
minimized
Source: Mosley (2005)
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