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)