Consideration of existing rainwater harvesting system and its enhancement using membrane filtration and uv irradiation

Pictures of the pilot of rainwater harvesting system a: Catchment roof, b: Storage tank .... Chapter 2 presents an overview of RWH systems with their history and also the components of h

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY

TRAN DIEU LINH

CONSIDERATION OF EXISTING RAINWATER HARVESTING SYSTEM AND ITS ENHANCEMENT USING MEMBRANE FILTRATION AND UV-IRRADIATION

MASTER'S THESIS Environmental Engineering

Hanoi, 2019

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY

TRAN DIEU LINH

CONSIDERATION OF EXISTING

RAINWATER HARVESTING SYSTEM AND ITS ENHANCEMENT USING MEMBRANE FILTRATION AND UV-IRRADIATION

MAJOR: Environmental Engineering

CODE: Experimental RESEARCH SUPERVISOR:

Principal Supervisor: Professor Jun Nakajima Co-Supervisor: Professor Naoyuki Kamiko

Hanoi, 2019

ACKNOWLEDGEMENT

First and foremost, I would like to express my heartfelt gratitude to my two brilliant supervisors, my main supervisor, Professor Jun Nakajima and my co-supervisor, Professor Naoyuki Kamiko To Professor Jun Nakajima: Thank you for accepting me

as your student and helping me to find out my interest in studies of rainwater treatment Thank you for your outstanding guidance, continuous inspiration and support in my two-year research I appreciate the in depth discussions which have sharpened my thought process and shown me how to transform my mistakes into skills To Professor Naoyuki Kamiko: Thank you for all the instructive advices and valuable knowledges you have provided me during my research work as well as my internship in Ritsumeikan University, Japan I am truly grateful to have such a fulfilling experience

working with you, which contributes no small part to my achievements

I am indebted to my mentor, Professor Jun Nakajima: Thank you for being a good mentor and for guiding me on the right path as well as providing me with the necessary materials and knowledges to work with my project Moreover, your creative ideas about the projects have impressed and inspired me a lot To be honest, you are not only

my respectable supervisor but also my beloved grandfather

In addition, I highly appreciate Professor Hiroyuki Katajama, Associate Professor Kasuga Ikuro, Doctor Nguyen Thi An Hang, Mrs Nguyen Phuong Thao and Mrs Dinh

Dieu Anh for their patience in guiding and assisting me through my Master course

I would also like to extend my appreciativeness to my fellow lab mates who have been working with me and sharing their experience and knowledge to me Thank you for all the joy, laughter and friendships to help me get over the stress of after-hours work and make my research much easier In addition, I would like to send my special thanks to

my classmate, Mr To Hoang Nguyen for his supports in my experiments and writing

CONTENT

Chapter 1 Introduction and objective 1

1.1 Background 1

1.2 Problem statement 2

1.3 Objectives 5

1.4 Structure of the thesis 6

Chapter 2 Literature review 7

2.1 Introduction of rooftop rainwater harvesting 7

2.1.1 Definition and history 7

2.1.2 Advantages and disadvantages of using rainwater harvesting 11

2.1.3 Components of rooftop rainwater harvesting system 12

2.2 Quality of harvested rainwater 16

2.2.1 Factors affecting rooftop harvested rainwater quality 16

2.2.2 Physico-chemical quality of rooftop harvested rainwater 16

2.2.3 Trace organics 19

2.2.4 Microbial quality of rainwater harvesting systems 20

2.2.5 Case study in Vietnam 24

2.3 Rainwater treatment and disinfection methods 26

2.3.1 Membrane filtration 27

2.3.2 Chemical disinfection 28

2.3.3 UV irradiation 29

Chapter 3 Methodology 31

3.1 Web survey of rainwater harvesting manuals in the world 31

3.2 Questionnaire survey of rainwater harvesting situations and people’s attitude 31

3.3 Examination of rainwater purification in a typical existing RWH 32

3.3.1 Sampling area 32

3.3.2 Commercial filter containing RO in combination with UV lamp 34

3.3.3 UV submersible germicidal System 36

3.3.4 Measurement of physicochemical quality 37

3.3.5 Measurement of microbiological quality 38

Chapter 4 Results and discussion 40

4.1 Web survey of rainwater harvesting manuals in the world 40

4.1.1 Purpose of using rainwater 40

4.1.2 Structure and materials for rainwater catchment roof 41

4.1.3 Design and material for gutter 43

4.1.4 Installation type and material for storage tank 44

4.1.5 Disinfection methods 46

4.1.6 Number of explanation contents 47

4.2 Questionnaire survey of rainwater harvesting situations and people’s attitude 48

4.2.1 Overlook of current situation in the area of study 49

4.2.2 Willingness to use our introduced rainwater treatment systems 52

4.3 Examination of rainwater purification in a typical existing RWH 54

4.3.1 Rainwater quality 54

4.3.2 Combination system of RO purifier and UV sterilizer 56

Physicochemical properties 56

Microbiological properties 58

4.3.3 Submerged UV lamp 59

Chapter 5 Conclusion 61

References 62

Appendix I 71

Appendix II 76

LIST OF FIGURE Page Figure 2.1 A cistern in Yerabatan Sarayi, Istanbul in Turkey 9

Figure 2.2 A common RWH system 13

Figure 2.3 Floating ball first flush diverter 15

Figure 2.4 Working mechanism of reverse osmosis filter 28

Figure 3.1 Sampling location of questionnair survey (Google Maps, 2019) 32

Figure 3.2 Pictures of the pilot of rainwater harvesting system (a: Catchment roof, b: Storage tank) 33

Figure 3.3 Design of DEWX RO AQUAPRO Serise AP-60 supplied by DEWX Vietnam 34

Figure 3.4 Sampling scheme of the examination of RO purifier in combination with UV lamp 36

Figure 3.5 Examination system of submerged UV sterilizer 37

Figure 4.1 Purpose of using rainwater (a: Total;b: Developing countries, c: Developed countries) 41

Figure 4.2 Different structure of roof 41

Figure 4.3 Materias for roof (a: Total; b: Developing countries; c: Developed

countries) 42

Figure 4.4 Shapes of gutter 43

Figure 4.5 Material for gutter (a: Total; b: Developing countries; c: Developed countries) 44

Figure 4.6 Type of tank ( a: Developing countries; b: Developed countries) 45

Figure 4.7 Materials for tank (a: Developing countries; b: Developed countries) 45

Figure 4.8 Disinfection methods(a: Developing countries; b: Developed countries) 46

Figure 4.9 Histogram of number of contents in a manual 47

Figure 4.10 Number of family member 49

Figure 4.11 Types of water used 49

Figure 4.12 Percentage of families use each type of water 50

Figure 4.13 Monthly water bill 51

Figure 4.14 Purpose of using rainwater 52

Figure 4.15 Types of water treatment 52

Figure 4.16 Willingness of residential people to use the introduced water treatement system( a: RO (4.000.000 VND); b: UV lamp (700.000VND); c: combine system (RO+UV)) 53

Figure 4.17 Microoganism concentration in Raw water (a: Total Coliforms; b: E.coli) 56

Figure 4.18 pH change through the system 57

Figure 4.19 Conductivity change through the system……… 57

Figure 4.20 Dissolved oxygen change through the system; Figure 4.21 Turbidity change through the system 57

Figure 4.22 Change in microoganism concentration through the system (a: Total Coliforms; b: E.coli 58Figure 4.23 Change in microoganism concentration vesus time interval (a: Total Coliforms; b: E.coli) 59

LIST OF TABLES

Page Table 1.1 Heavy metal concentration in tap water districts in Hanoi 5Table 2.1 Concentration of E.coli in storage tanks of roof-harvested rainwater (adapted from K Hamilton et al, 2018) 21Table 2.2 Chemical and microbiological characteristic of harvested rainwater before and after treatment 24Table 3.1 Components of DEWX RO AQUAPRO Serise AP-60 supplied by DEWX Vietnam 34Table 4.1 Quality of rainwater in storage tank 54

CHAPTER 1 INTRODUCTION AND OBJECTIVE

1.1 Background

For thousands years, through big cities to deserts, human has fought to sustain oneself

by the management of vital, especially water It is clear that water is one of the cardinal resources in the world which takes an important role to ensure the live of all spices and propose a part of larger ecosystem (Connor, 2015) In addition, one of the important index indicating the development of a country is the sustainability of water (Villholth

et al., 2010) According to the definition of European Union (EU) Water Framework Directive (WFD), “Water is not commercial product like any other but, rather, a heritage which must be protected, defended and treated as such” It is possible to predict the availability of water in the natural water cycle without the interference of human However, because of human activities and intrusions including wetland drainage, deforestation as well as other means of pollution, the ecosystem and natural sequence have become unbalance As a result, the world is now facing various water related issues and it has been reported that one third of population in the word is now facing the consequence caused by water scarcity (De Silva et al., 2007) Beside the issues of water availability, the issues of available water quality are even more critical Water scarcity and pollution issues lead to health issues due to the water borne disease exposure In the case water stress occurs, people would consume any source of water they can reach without confusing of water quality, in this case, lack of water leads to lack of water quality In a study in 2007, Alcamo and colleges analyzed a scenario exploring the change to 2050 in average annual water availability According to the observed results, precipitation in many parts of the world was predicted to increase leading to the growth in water availability in these areas On the other hand, increasing

air temperature also results in the increase of evapotranspiration, consequently water availability reduces The evapotranspiration and precipitation interact differently on water availability in both positive and negative way, however the evapotranspiration was proofed to overshadow the increase in precipitation because the temperature increases almost everywhere in the world (Alcamo et al., 2007) It is clear that climate change put a lot of visible effects on the limitation of water In addition, the improvement of socioeconomic condition increase the population day by day, meanwhile the more the world develops the more water is required In this condition, what will happen to water supply and demand? How to make the situation of water resource better?

For that reason, toward the sustainable development of our earth, the sustainability of water sources is needed Since 4500 B.C, rainwater harvesting (RWH) system had been popularly applied in the southern Mesopotamia (Iraq) inhabitants and inhabitants from other Middle Est countries After thousands years, the use of this type of water has become more and more interested in both developed countries and developing countries, from rural area to urban area By applying RWH systems, human can control storm water runoff to natural reservoirs and depressions as well Furthermore, other usages of rainwater are supplying household water including drinking water and irrigation water as well as injecting into the ground in order to replenish supply of groundwater Moreover, by using in-situ harvested rainwater, carbon footprint caused

by water collection and distribution can be reduced and the cost of transporting water reduces as well (Harb, 2015)

1.2 Problem statement

World Health Organization (WHO) reported that 783 million in the world, about one per 10 people cannot access to improved water Furthermore, around 2.5 billion people – more than one third of planet population still lack proper sanitation This problem is

specially serious in Asia, where is home of around 4.5 billion people Compare to other areas in the world, Asia countries are now in the worse condition than other parts in the availability of water according to UNESCO report The water availability in Asia area only counts for 36% of the total water in the world meanwhile 60% of the world population is in this area (World Water Assessment Programme, 2003) Positively, among the number of people accessing to safe water, 47% are from China and India due to the economic growth and consideration on standard of living in both nations Located in Asia’s Southeastern part, Vietnam is home of over 86 million people with

$3100 of estimated GDP per capita Almost two-thirds of Vietnam population lives along three main river basins of the country, which are Dong Nai, Mekong Delta and Thai Binh The country has 10km of rivers in total consisting 2360 rivers, therefore the amount of water supply seems to be enough for the nation (The Water Project, 2019) However, because of the limited financial capacity and the lack of infrastructure along with an uneven rain distribution, many parts of Vietnam still have to deal with water shortage situation Despite of the improvement in water supply infrastructure and management recently, the situation in many rural parts of Vietnam which are often the poorest area of the countries has not been improved so much I has been reported there

is only 39% people living in the rural area can access to improved water and sanitation

In some recent decades, the rural residents have changed from surface water obtained

in shallow dug well to the pumped groundwater from private tube wells (The Water Project, 2019) In the peri-urban area of Hanoi and several communities locating in the Northern part of Vietnam, arsenic contamination has been reported in the drinking water which is supplied from groundwater source (Agusa et al., 2006; Nguyen et al., 2009) Millions people living in these area have a severe risk of arsenic poisoning High concentration of arsenic can cause cancer, skin and neurological problem for human Furthermore, the recent rapid economic development in the country causes serious stress on river water quality due to the increase in various toxic compounds

discharged The rivers surface water is locally contaminated by organic pollutants such

as oil and solid waste discharged from industries and livestock activities In addition, the special geography and topography of the country also lead to several hazards including storms, floods, typhoons and drought These hazards result in many water issues such as waterborne diseases and water pollution which may put impacts on livestock and agricultural lands and the nation’s public health According to a report of the Ministry of Natural Resources and Environment, 80% of the diseases caused for Vietnamese are waterborne diseases The popular waterborne diseases found are dysentery, malaria, typhoid and cholera There is no doubt that in Vietnam, agriculture consumes the highest amount of water because this country is one of the largest provider of rice in the world More than 80% of water production is used for agriculture Water resources are significant resources because they are not only natural sources but also sources of economic, social as well as cultural activities In recent decades, the government of Vietnam has attempted to develop water resources management issues by implementing related policies and programs However, there are still some challenges including improving access to safe water and clean sanitation in both urban and rural area, improving public participation, knowledge as well as strengthening management of river basin According to the data collected in 2015, 98%

of Vietnam total population can access to clean water, which means that nearly 2 million people in the country still cannot access to clean water, especially in the rural areas (WHO/UNICEF, 2015)

Regarding the quality of current water supply in Hanoi, Vietnam, Table 1.1 presents the situation of water supply in some district in Hanoi in parameters of heavy metal

Table 1.1 Heavy metal concentration in tap water districts in Hanoi

District

Concentration of heavy metal (ppb)

Hoan Kiem 12.2 0.2 13.5 2.5 66.4 12.8 ND 10.4 6.1 0.1 2623 Dong Da 1 2.4 0.3 21.8 23.6 123 5.5 ND 16.5 7.1 0.4 60 Dong Da 2 11.8 0.3 15.3 14.6 96.9 4.2 ND 12.6 6.9 0.4 94.1

Ha Dong 9.1 0.3 17.3 10.1 136 62.2 0.2 12.3 7.8 ND 554 Hoang Mai 20.7 0.8 15.0 17.3 217 234 0.2 11.5 31.2 0.2 444

Tu Liem 0.8 0.2 14.6 4.9 67.6 7.4 ND 11.7 6.2 ND 23.5 Gia Lam 1.1 0.2 15.6 7.5 111 5.1 ND 11.7 6.9 ND 69.9 For a short conclusion, the country is gradually getting into a water scarcity scenario and tenable ways are needed to strengthen the availability of water

1.4 Structure of the thesis

This Thesis comprises of 5 chapters In the first chapter, the certain key aspect of this study is generally introduced The chapter starts with a brief background of global water cycle and distribution followed by the problem statement and the objectives as well as the expected contribution of the study The structure of this thesis is given at the end of chapter 1

Chapter 2 presents an overview of RWH systems with their history and also the components of harvesting systems followed by the quality of rainwater harvested and treatment methods for purposes of use

Chapter 3 explores the methodological framework of the study including sampling strategy and questionnaire surveys with residents in the area of research

Chapter 4 focuses on analyses of obtained results in this research and the discussion of the analyzed results

Chapter 5 is the last chapter of the study and it gives the conclusions observed from the results in chapter 4 Recommendations and prospects for the future are also part of this chapter

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction of rooftop rainwater harvesting

2.1.1 Definition and history

Definition

The concept of “Rainwater harvesting” simply involves all those techniques of collection and storage rainwater in natural reservoir or tank for subsequent utilization rather than of allowing it to run off The term has been used to accumulation and storage of rainwater in mini-scale resources of water; in addition this term refers to the activities with purposes of harvesting surface and other hydrological studies and engineering interventions regarding the limited water enforcement (Patel et al., 2014) Rainwater is normally collected from the roofs of buildings or from other impermeable surfaces Therefore, rooftop water harvesting (RRWH) is considered as an important sub set of RWH This study covers only rooftop RWH

History

It has been written in history that rainwater collection and storage techniques have started to be applied since thousands of years when human first started to farm the land and new methods of irrigating crops were required However, there are many changes have taken on materials and design of harvesting systems through thousands years to improve the performance of harvesting rainwater

Archeological evidence showed that the concept of RWH and evidence of this green technology may trace back more than 4000 years The use of cisterns for rainwater storage can date back to the Neolithic Age In Southwest Asia, by late 4000 B.C, waterproof lime plaster cisterns were built largely to keep rainwater for farming In

India, Mesopotamia, China, and Israel, rainwater was captured as early as 2.000 B.C Harvesting technologies in the Indus Valley were extremely advanced In many ancient cities in Indus Valley which still remain today, it is easily to find huge vats cut into the rock for accumulation of rainwater During dry time of the year, these vats were used

to keep the citizens and local agriculture going (Gupta and Agrawal, 2015) By that time, the basic design of RWH systems includes a large rock formed into a basin using clay and other rocks to seal it from leaking The storage cisterns for hillsides runoff water employed to agricultural and domestic use still remain today Additional evidence of RWH via an extremely large cistern in Jerusalem since 2500 B.C has been found Dating back to 1700 B.C, other evidence of large cistern were also found in the Greek Isles (Rotoplas, 2018) In the southwest United State, Anasizi and other Native American ancient residents used to allow rainwater flow into the villages or cliff dwellings for livestock activity and drinking; the water flowed following the natural contours of plateaus and mountains by the carefully crafted purveyance trenches Meanwhile, in the North America cultures, because of rainwater softness whereas groundwater shows high hardness, it was early gathered rainwater in barrels for daily activities such as bathing, laundering and other cleaning chores (Gould and Nissen-Petersen, 1999)

In most of ancient cities, including Roman, the urbanization and increase of population led to the increase in demand of water for housing including both potable and non-potable purpose As a result, covered cisterns had developed The cisterns were constructed underneath the courts The underground design shows two main advantages: firstly, this kind of cistern increases the volume of rainwater stored and decreases the evaporation losses of water inside tank Secondly, by applying underground cisterns, rainwater inside can be protected against pollution In rain event, all the rainwater from the rooftops ran into the pools then the overflow flowed into the cisterns By that time, the harvesting techniques were decentralized and this is

considered as the reason why RWH lost their momentum with the increase of use and the development of a centralized supply from spring channel into the urban areas However, it is uncommon to see centralized RWH and storage in cistern The largest cistern in the world is found in Yerabatan Sarayi, Istanbul in Turkey The cistern was built by Byzantine Emperor Justinian I (527-565 A.D) and named as arasında Yerebatan Palace and measures 140 by 70 metres The capacity of storage is 80.000 m3 The underground structure is based on intersecting vaults

Figure 2.1 A cistern in Yerabatan Sarayi, Istanbul in Turkey

Another other cistern with high capacity of 50.000 m3 was also found named Binbirdik There is a document suggests that Binbirdik was built under Caesar Constantine (A.D

329 – 337) Both above cisterns are centralized storage In this systems, rainwater was collected from paved streets and roofs and a sophisticated system of filters assured clean water (Hasse, 1989) However, the systems like cisterns in Istanbul is no longer used in and only considered as examples of centralized RWH systems Two main reasons for the lack of use of this system are proposed: firstly, the construction cost of underground cisterns is higher than the construction of the above one; secondly human excrete can cause pollution for the water storage in underground cistern

Although RWH systems with closed cisterns were not favored in other reasons as in ancient Rome, sometime they were still found in the semi-desert areas at home scales where the owners did not want to build wells or springs in their house The Christian monks also built monasteries with this kind of system Other examples of closed cisterns system were found in monasteries in Mexico and in former Spanish Empire These above example of such a complicated system proof the high quality of design and construction in ancient time

However, the use of RWH system became less favorable following the increase of urbanization The assumed reason is that during the industrial age, larger amounts and higher quality of water were required, safe water suppled via pipes are more popular But supplied water not only shows advantages but also have a lot of disadvantages as following:

- In the bad natural conditions for example earthquakes, or because of the destruction caused by war as well as source pollution including environmental pollution through chemicals); the supply of water will be totally cut-off

- The convenience access of supply water leads to the wastage of using water, it is understandable In addition, water which is one sources of life has become a commodity of consumption and also played the contradiction between suitable management of water and economy expansion

However, in urban areas nowadays, it is hard to find an alternative to a centralized water supply

After thousands years, RWH is once again gaining importance in human life in rural areas particularly in developing countries due to the increase in water demand which requires all possible sources of water (Climateincorp.com, 1996)

2.1.2 Advantages and disadvantages of using rainwater harvesting

Advantages of using rainwater

The use of rainwater shows many benefits over supplied water and ground water First

of all, it is easy to maintain the water and harvesting system Simple technology can be employed to construct this type of system The overall cost for installing and operating

is much lower than that of water pumping system As a result, RWH is a sustainable choice for source of water In addition, rainwater can be storage in cisterns for use during time meanwhile supplied water can be cut-off in some special conditions Secondly, for many households and small businesses, using rainwater even for non-drinking purpose of drinking purpose can reduce their water bill For industrial scale and large business, harvested rainwater can also be used for many operations instead of depleting the nearby water sources Thirdly, the population increases leads to the continuous increase in water demand As a result, high amount of groundwater is extracted to fulfill the daily life Therefore, groundwater which has gone to significant low level in some areas where there is huge water scarcity depletes By using rainwater, the need of groundwater can be decreased In addition, it has been reported that RWH system results to reduce soil erosion and floods In low lying areas, collecting water in storage cisterns can reduce floods Moreover, soil erosion and surface water contamination by pesticides and fertilizers from run-off of rainwater can also reduce, hence lakes in ponds can be cleaner Finally, although there are some studies recommend that rainwater before treatment cannot be used for drinking, rainwater can

be used for many different non-potable purposes From chemical contamination aspect, rainwater is free from many chemicals which are found in groundwater, therefore, rainwater is suitable for watering gardens and irrigation In the areas where have to commonly face to forest fires and bush fires in summer, storing rainwater in large

reservoir can be considered as a wonderful idea In addition, collected rainwater can also be used for toilets flushing, washing house and clothes etc

Disadvantages of using rainwater

Although there are many advantages of using rainwater, some disadvantages also exist Unpredictable rainfall is a biggest drawback of harvesting rainwater It is hard to predict rainfall and the supply of rainwater can be limited because of little or no rainfall Rainwater use is suitable in the areas with high level of rainfall Second disadvantage is requirement of regular maintenance because rainwater in cisterns is easy to get prone to mosquitoes, rodents, insects, algae growth and lizards The tanks can become as good environment for many insects and animals if they are not maintained properly Third, if the materials chosen for roof, gutter, pipe and tank are not safe and suitable to the area condition, microbiological and physicochemical pollution can occur easily Forth, rainwater requires large storage tank to reach the demand of use during year, it takes a large area in the house

RWH system is gaining speed over time, especially in the areas with plenty of rainfall

(Conserve Energy Future, n.d)

2.1.3 Components of rooftop rainwater harvesting system

Historically, principle of rooftop RWH system is quite simple: rainwater run from roofs to tanks A common RWH system contains four main components: (1) catchment surface (roof), (2) conveyors followed by (3) filter and (4) storage tanks (J Song et al., 2009)

Figure 2.2 A common RWH system

Below is a brief overview of each component

(1) Catchment surface

The performance of rainwater catchment highly depends on texture of the catchment The smooth and impervious surfaces lead to better water quality Waterproof materials which absorb less water and do not give chance for microbes and dirty particles to accumulate in the pores and seams may give better quality of water harvested In addition, the smoother the surfaces are, the faster rainwater flows through and the cleaner the surfaces are For the best quality of water generated, suitable materials are clay, metal and concrete There are several types of roofing material which are not suitable for rainwater due to components leaching For example, roofs made by copper

or affected from fungicides, pesticides and herbicides are warned not to be employed Furthermore, untreated metal such as galvanized roofs are not appropriate to the roof material because zinc leaching can cause harmfulness to vegetation Because rainwater can dissolve minerals in catchment surface components then carry them flowing to the storage system Rainwater harvested forward potable purpose should not runoff from

roofs which contain untreated metal including copper, zinc coatings, asbestos or contaminated by lead flashing, lead-based and other harmful chemicals as well as biocide compound

(2) Conveyance

Another important component of the system is conveyance which channels rainwater from catchment area to storage area by gutters connected to downspouts Half round gutter are prefer to the square and V-shape one because it display high performance in avoiding joint seams in the system to reduce debris catching and bacterial and algae growing Regarding structure, an outer edge higher than roof-side edge and has splash guards of roof valleys and slope towards downspout is highly recommended To reduce the debris accumulating in the angle then blocking the flow, angle in downspout pipe should be less than 45 degrees The most common material for gutter and downspout are metal and PVC, in some lower income area, bamboo and wood are also options

(3) Pre-filter and first flush

Rainwater runs from catchment surface can pick up debris and leaves on the way Therefore, pre-treatment items should be included in the system before water runs into cisterns Debris excluder of similar filter can prevent the accumulation of needles, leaves and other debris Moreover, to larger debris, rainwater can dissolve or pick up materials too fine for the screens to filter out In order to catch these pollutants, when any rain event occurs, the very first part of rainwater running from the catchment area should be diverted from the storage tank, the diverter is called “first-flush” diverter The “first-flush” water contains the highest concentration of debris, pollen and animal feces as well as pesticides and other airborne residues

There are several types of diverters which can be employed, all of them need to be installed before the storage tank The design of diverter can be very simple which has a PVC standpipe in connection to a downspout The simplest first-flush diverter consists

of a PVC standpipe connected to a downspout In this design, the standpipe play role as

a storage device for collection of initial rainwater runoff, cleaner rainwater will run into the tank after it fills up There also is a ball-valve system for first-flush which has similar mechanism to standpipe first flush but it has a floating ball to seal off the diverter pipe’s top when this pipe is full, then cleaner water flows into the tank More advanced first-flush designs can consist removable filter inserts providing additional filtration

Figure 2.3 Floating ball first flush diverter

(4) Storage

There are many available options for material of storage tanks including stone, steel, plastic, fiberglass or concrete, ferro-cement which is steel-reinforced cement They should be durable, opaque and able to withstand the standing water forces, they also should be watertight, smooth inside and clean Tanks should be covered tightly to prevent insects, bird or frogs entering and mosquito breeding Storage tanks can be constructed underground or aboveground, the size and types are based on several variables such as: quality of rainfall, water use demand, time interval of rain events,

runoff coefficient of catchment surface, space availability and affordable budget The tank with large capacity which is greater than 4000 litters is called cisterns meanwhile the term of “barrel” is for tank with capacity smaller than 400 litters To increase storage capacity, several barrels can be linked together

2.2.1 Factors affecting rooftop harvested rainwater quality

Rainwater quality highly depends on source of water and other factors during accumulation, treatment and storage before reaching to the consumer Contamination can occur at any stages of the harvesting system including roof, conveyance system and storage tank depending on the contaminated status and material of each component

It has been reported the factors affecting runoff from roof, which are below (Forster et al., 1996; Martinson et al., 2009; Sarikonda et.al., 2010; Gwenzi et al., 2015):

(1) Roof and conveyance material: physical characteristic including weather ability, surface coating, roughness and age as well as chemical characteristic

(2) Size and slope of the roof

(3) Material and design of storage tank

(4) Rainfall event: wind, intensity of rainfall, pollutant concentration in the source

of rain

(5) Meteorological factors: antecedent dry time, weather characteristic when rain event occurs

(6) Pre-filter (“first flush” diverter) application

2.2.2 Physico-chemical quality of rooftop harvested rainwater

There are various reports from several parts of the world mentioning the chemical characteristic of roof runoff have been published Most of these reports

physico-indicated that physico-chemical quality of rainwater are acceptable for potable purpose (Chang et al., 2004; Simmon et al., 2001; Dinrifor et al., 2010) It was pointed out that difference between roofing material, treatment and orientation as well as design of roof lead to the wide variations in concentration of several metals including sodium, potassium, calcium, magnesium, sulfates, chlorides and especially nitrates (Gwenzi et al., 2015) Rainwater itself is lightly acidic with measured pH from 4.5 to 6.5, however after falling on the roof and running into the tank as well as storage time, pH slightly increase (Charlson and Rodhe, 1982) According to a study of Islam and many other studies (Islam et al., 2010), tanks constructed from ferrocement may increase pH of rainwater, this type of material is normally employed in developing countries However,

pH value reduces through age of tank and storage time (Meera and Ahammed, 2006) Meanwhile, application of wooden roof lowers pH of harvested water (Chang et al., 2004) The season for this phenomena is that rainwater falling on the roof can be trapped into wood shingle’s roughness and cracks allowing growth of plants and decay

of organic matter, as a result, more H+ ions are generated which reduces pH of water Nevertheless, some other studies reported that there is no significant difference among rainwater qualities observed from different design and material of harvesting system (Meera and Ahammed, 2006)

Several cations and anions have been detected from rainwater sample such as sodium, potassium and calcium, sulfates, chlorides and nitrates, among them, sodium and calcium show highest concentration (Junge and Werby, 1958) The differences within materials for harvesting system clearly pointed out that ions initiated from material chosen; fibrous cement roof releases more calcium meanwhile concrete tiles show higher concentration of both calcium and potassium (Forster et al., 1998) Regarding other chemical and biological parameters like COD and BOD5, these parameters don’t change with the change in different materials including zinc, interlocking tiles, flat tiles and slate (Meera and Ahammed, 2006) In addition, different concentration of NH4+

and Cl2 could be observed with the change in season and roofs affected by local emission showed elevated suspended particle (Forster et al., 1998)

One of the most interested indicators of rainwater is heavy metal concentration because

of the toxicity and the fact that these metals are difficult to be removed or transformed

by simply treatment processes (Montero Alvarez et al., 2007) The main source of heavy metals in rainwater is attributed to material of catchment area Zinc and copper are most commonly found in rainwater harvested from metal roofs (Forster et al., 1998) High concentration of Zinc and Copper were considered as an environmental hazard (Chang et al., 2004) Lead and cadmium are also detected in rooftop runoff (Thomas and Greene, 1993; Rattonetti, 1974) Polyester roof, slate roof and galvanized iron roof are indicated as the sources of lead, meanwhile zinc and cadmium were proofed to be released from zinc roof (Gromaireet et.al, 2002) The erosion of zinc roof and gutter are the main reason for releasing Zinc, Cadmium is also a minor component of zinc roofs The presence of zinc was also found in rainwater harvested from galvanized iron roof, however the concentration far lower than WHO standard (Ghanayem and Box, n.d) It is also found by Chang and colleges (Chang et al., 2004) that concentration of zinc from old roof is significantly lower than from the new one Furthermore, presence

of some other metals like manganese, aluminum and iron were also reported (Penkett

et al., 1979; Lee et al., 2012) The pH of rainwater also contributes to leaching of heavy metals from harvesting system It has been reported that lower pH leads to higher lead concentration In addition, when pH decreases, the concentration of heavy metals like zinc, copper and lead also reduce (Meera and Ahammed, 2006) For the safety of using rainwater especially for drinking purpose, it is important to monitor the presence of heavy metal in rainwater, particularly runoff from metal roofs However, there are not many studies reporting on the heavy metal quality of rainwater in developing countries

2.2.3 Trace organics

Another important group of pollutants in roof runoff is trace organic compounds Many

of studies have indicated that concentration of pesticides as trace organics in rainwater

is higher than standard for drinking water according to standard of WHO (Meera and Ahammed, 2006) Chemical properties of organic pollutants and characteristic of roof are main contributions to concentration of trace organics (Forster et al., 1998) Studies

on tar paper covering material for roof reported that rainwater falling on this material contain toluene and other petroleum hydrocarbons (Gessler and Sparks, 1963) Other studies indicated high level of organic carbon for a polyester roof especially in the first millimeters of runoff depth However, polyester roof is only a good conveyance for organic compounds, meanwhile gravel and tile roofs retained them (Meera and Ahammed, 2006) One of the most popular carcinogen found in urban ambient air and water is polycyclic aromatic hydrocarbons groups (PAHs) which is released from incomplete combustion of fossil such as petroleum, oil and coal According to Forster the main PAHs found in roof runoff are fluoranthene and pyrene PAH level bases on the area of rain catchment and roofing materials In the industrial or urban area, the concentration of PAHs found is higher than in other area There is also interesting point that the concentrations of PAHs on different side of the roof are difference The attributed reason is the changes in speed and direction of wind and photodecomposition lead to the difference in received net precipitation (Forster, 1999) In another study on quality of rainwater, Forster and colleges also reported the values standing for adsorbable organically bound hydrocarbon which is called AOX This parameter was found high in runoff from roofs receiving local emissions AOX values also change with the change of season In summer, AOX values calculated are lower than in other season (Forster, 1998)

2.2.4 Microbial quality of rainwater harvesting systems

In the field of RWH, microbial quality of harvested rainwater have been interested by researchers around the world The upcoming table presents microbial quality of roof-collected rainwater in several areas According to the table, numerous studies clearly proof that the microbiological quality of rainwater do not often reach the standard for drinking water It was concluded that the cleanliness of the roof take an important role

in harvested rainwater (Ahmed et al., 2008, 2011b, 2012a)

Animal like birds, rats, possums and squirrels and insects including flies, mosquitos can leave fecal matter on the surface of catchment area As a consequence, the roofs become good environments for the growth of virus, bacterial and protozoan pathogens which may contaminate the runoff from rooftop It was demonstrated in the study of

rainwater in Southeast Queensland, Australia that Escherichia coli (E.coli) in identical

biochemical phenotype profiles occurs in rainwater storage tanks and in animal feces According to these results, feces could be considered as the main source of E coli in harvested rainwater (Ahmet et al., 2012a) However, there are also several studies reported that the microbiological quality also bases on roofing materials According to these researches, quality of rainwater from roofs made of metals is better than from other material, the reason is metal surface is easier to be heater under bright sunlight, the high temperature obtained increase the efficiency of killing bacteria (Yaziz et al., 1989; Ghanayem and Box, n.d) Yaziz also reported that longer distance between rainfall events causes to the increase in microbiological contamination and the intensity

of rainfall also affects the rain quality (Yaziz et al., 1989) Storage time also affects the microorganism growth situation However, the reported changing trend in microbiological quality after different storage time intervals is still in conflict Some studies reported the increase in number of bacterial during storage, meanwhile other studies concluded the reversal trend (Meera and Ahammed, 2006) According to a review of Meera, number of Pseudomonas and Aeromonas grew 2 log from 1 CFU/mL

to 100 CFU/mL during storage in one study in 1989 However in another study conducted in 2001, it was reported that faecal Coliform and Total Coliforms as well as faecal streptococci reduce strongly during storage tank An extra interesting finding is that the tank size also contributes to the microbiological quality The smaller the tank is, the higher in the number of microorganism Because in the tank of lower capacity, contamination of microorganism takes more opportunities to extend In addition, in smaller tanks, it is easier for sludge to accumulate at the bottom then become good environment for growth of bacterial (Meera and Ahammed, 2006) Therefore, the application of first flush should be widen to reduce the risk of microorganism

Table 2.1 Concentration of E.coli in storage tanks of roof-harvested rainwater (adapted from K Hamilton et al, 2018)

Country Methods used No of

samples tested (%

of sample positive)

Mean concentrations ±

SD or range (CFU, MPN, or GC/100

Spread plate method Membrane filtration

205–10,000 CFU

Ahmed et al., 2008 Lee et al.,

2010 Hamilton et al., 2016

filtration/Colilert QuantiTray (IDEXX) Membrane filtration Membrane filtration Membrane filtration Membrane filtration Membrane filtration Membrane filtration

0–75 CFU 1->687 MPN 1->99 CFU

35 CFU 0–6000 CFU 0–20 MPN

Leong et al.,

2017 Waso et al.,

2016 Ahmed et

al, 2014 Ahmed et

al, 2012

Ahmed et

al, 2010 Ahmed et

al, 2012 Sazakli et al., 2007 Dobrowsky

et al., 2014 Levesque et al., 2008

USA

USA

11 (0)b 8.8 ± 5.9 MPN

Kaushik et al., 2014 Hamilton et al., 2017 Pinfold et al., 1993 Horak et al.,

2010 Islam et al.,

2011 Kris et al.,

2017 Jordan et al.,

2008 NM: not mentioned

a: Summer sampling; b: Winter sampling

CFU: Colony forming units

GC: Gene copies

MPN: Most probable numbers

2.2.5 Case study in Vietnam

A research on a case study in rural Vietnam was conducted from August 2014 to July

2015 to evaluate the current situation of rainwater quality and discuss potential parameters of water quality for drinking purpose The pilots of harvesting system in this study located at two schools in rural Hanoi, Vietnam The system components are galvanized iron roof, PVC gutter, first flush diverter and stainless tanks with mosquito nets For the treatment purpose, physical filter and UV sterilizer are employed

Chemical and microbiological characteristic of harvested rainwater before and after treatment are presented in table 2.2 below (Lee et al., 2017):

Table 2.2 Chemical and microbiological characteristic of harvested rainwater before and after treatment

No ordor

No ordor

According to the above results, the physicochemical properties of harvested rainwater

in the area of study meet the standard of both Vietnam national standard and WHO standard for drinking water However regarding microbiological aspect, rainwater

shows higher level of Coliform and E.coli in comparison to the standards The employed treatments show good performance in killing bacteria, Coliforms and E.coli

in treated samples are non-detected

The quality of harvested rainwater can meet the standard for non-potable purpose of use However, for drinking purpose, the microbiological should be at zero Therefore, appropriate treatment should be applied in RWH systems before use This dissertation pays attention of three different methods of disinfection including membrane filtration,

chemical disinfection and UV irradiation Detail mechanism as well as benefits and drawback of each method is presented following

Osmosis is a natural phenomenon providing water to all animals and vegetable cells to support life Literally, water moves from lower concentration of solute (higher concentration of water) to a higher concentration of solute (lower concentration of water) across a semi-permeable membrane This means that water can cross a selectively permeable membrane from a dilute solution to a concentrated solution A semi-permeable membrane is a membrane which allows only certain molecules or ions

to pass through Osmosis occurs naturally without energy applied, but to reverse the process, energy is required A reverse osmosis membrane is a semi-permeable membrane that allows the passage of water molecules but not the majority of dissolved salts, organics and bacteria However, to do this, water need to be pushed through the reverse osmosis membrane by applying a higher pressure than it of naturally osmotic Similar to micro filtration, reverse osmosis filtration can increase the water quality in both physicochemical properties and microbiological properties Pretreatment is often

required before RO membrane but with the good physical quality of rainwater, pretreatment is not necessary The most important disadvantage of using this type of filter is that the membrane is easy to be damaged therefore requires regular maintenance (Separationprocesses.com, n.d)

Figure 2.4 Working mechanism of reverse osmosis filter

2.3.2 Chemical disinfection

According to several reports, Chlorine is considered as the most favorable chemical disinfection methods for supplied water which shows good performance in bacteria killing therefor reduces the health risk of water Chlorine is used in both liquefied gas phase and sodium hypochlorite solution (NaOCl)

This method is popular due to its easy application as well as the low cost of use and no maintenance required However, the employment of chlorination can negatively affect human health, problem regarding skin, hair, eye and other body parts can occurred after exposer of chlorine during treatment duration and residual chlorine concentration

in treated water Another drawback is that various types of viruses cannot be treated by

chlorine Furthermore, natural organic matter (NOM) can react with residual chlorine

to form byproducts like trihalomethanes (THMs) which is dangerous carcinogen (Cantor et al., 1998)

2.3.3 UV irradiation

Ultraviolet (UV) energy is invisible radiation locates in the electromagnetic spectrum between x-rays and visible light In other words, UV spectrum shows smaller wavelength than visible light and larger wavelength than x-rays The most common sources of UV radiation is sunlight with three main types of UV lights: UVA, UVB and UVC UVA rays express lowest energy with longest wavelengths (400 nm - 320 nm), followed by UVB (320 nm - 290 nm) rays and UVC (290 nm - 100 nm) rays with shorter wavelengths Among them, UVC light show best performance in disinfection

A mercury arc lamp with low-pressure are often employed as the source of UVC light (254 nm) in UV water purifier Application of UV sterilizer in water treatment can reduce almost microorganisms and virus except some higher dose required organism (protozoa, most molds and cysts of Cryptosporidium and Giardia)

UVC radiation kills microorganisms by altering the DNA in virus and bacteria cells and preventing reproduction of these cells UV sterilization cannot remove organisms from the water but merely inactivates them Once UV radiation exposes to the cells, the nucleic acid in the cells ends up noticeably harmed by because of the formation of covalent bonds As a result, DNA cannot duplicate, consequently, they cannot reproduce Although UV light play good performance in killing bacteria and virus, there are some disadvantages of using this method in water treatment UV light can only kill bacteria at one point in the system of watering and there is no residual germicidal effect downstream That means, if there is only one survival bacteria after disinfection time, they can reproduce in storage water Moreover, killed cells are not removed from treated water then can become a nutrient environment for any bacteria