Introduction and objective
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).
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
Concentration of heavy metal (ppb)
As Cd Cr Cu Fe Mn Mo Ni Pb Se Zn
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.
Objectives
1 To clear the situation of RWH around the world and compare between developing and developed countries
2 To clear the current situation of RWH and people's attitude in a peri-urban area in Hanoi, Vietnam
3 To clear the applicability of existing water treatment devises to RWH for reduction of pathogenic risk.
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.
Literature review
Introduction of rooftop rainwater harvesting
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
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 m 3 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 m 3 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
Quality of harvested rainwater
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 physico- chemical characteristic of roof runoff have been published Most of these reports 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 BOD 5 , 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 NH 4 + and Cl 2 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
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)
Spread plate method Membrane filtration
Membrane filtration Membrane filtration Quantitative PCR Membrane filtration Membrane filtration Membrane filtration Membrane filtration
Membrane filtration/Colilert QuantiTray (IDEXX) Membrane filtration Membrane filtration Membrane filtration Membrane filtration Membrane filtration Membrane filtration
4–800 CFU 3–5011 CFU 3–2290 CFU 22–10,964 GC 0–3060 CFU 1–230 CFU 0–250 CFU 0–250 CFU
Dobrowsky et al., 2014 Levesque et al., 2008
2008 NM: not mentioned a: Summer sampling; b: Winter sampling CFU: Colony forming units
GC: Gene copies MPN: Most probable numbers
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
Vietnam WHO Median Range Median Range pH 6.5-8.5 8.2-
Odor No odor None 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.
Rainwater treatment and disinfection methods
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
Herein two outstanding filters are discussed for disinfection of rainwater: microfiltration and reverse osmosis
Micro-filtration working mechanism bases on the separation of dissolved substance in water into membranes according to molecular size Therefore, micro-filtration shows outstanding ability in turbidity and other chemical and physical pollutants removal In addition, micro-bacterial can be removed by this type of filter Beside, micro-filer has some disadvantage such as the membrane fouling often occur which reduces the performance of equipment and asks for expensive maintenance, moreover, shear sensitive materials can be damaged because of high flow rates (Separationprocesses.com, n.d)
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)
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 which survived after irradiation In addition, mercury lamp is also a risk of heavy metal leaching in the system (Oram, 2014).
Methodology
Web survey of rainwater harvesting manuals in the world
From websites 34 RWH manuals of 13 countries and area were downloaded from May
2018 to February 2019 The manuals cover both group of developing and developed countries as shown in Appendix I The main work of this part is making comparison between manuals designed for developing countries and developed countries in different aspects The compared aspects list below:
(1) Purpose of rainwater use, for potable or non-potable purpose
(2) The system design including structure and material of roof, gutter, pipe and tank
(5) Leveling the clear level of manuals
The contents data in the manual were categorized according to the above aspects to 2 to
5 categories and compared between developing and developed group.
Questionnaire survey of rainwater harvesting situations and people’s attitude
The survey was taken in Yen Nghia commune, Ha Dong district, Hanoi, Vietnam with google map picture at Figure 3.1 Ha Dong is a Southern urban district of Hanoi with natural area is 4.833,7 ha and population is 352.002 reported in 2018 Ha Dong is in the climate regime of Red river Delta, influenced by the sea breeze, is hot and humid and cold season is affected by the Northeast monsoon, with average annual temperature of 23.8 o C, average rainfall 1700 mm - 1800 mm (Hadong.hanoi.gov.vn, 2013) The residential people have used RWH for long period Compared to the center of Hanoi the house density is lower and house area is generally larger with garden
In the commune 50 households were picked randomly to answer the questionnaire on current situation of water usage including RWH The questionnaire included personal information, house area, water usage (type of water using, monthly water bill), RWH situation (purpose of use, water treatment method, cost), willing to pay (commercial filter system, UV lamp) The detail contents are shown in Appendix II
Figure 3.1 Sampling location of questionnair survey (Google Maps, 2019)
Examination of rainwater purification in a typical existing RWH
A pilot of RWH system is set up at a residential household in Ha Dong district, Hanoi, Vietnam The total area of the house including building, yard and garden is 400 m 2 There are 5 peoples living in this family who consume 20m 3 of water each month The main sources of water used are supplied water, groundwater and harvested rainwater
Many years ago, the family use rainwater as potable water However recently, because of the fast urbanization of the district which leads to the increase of constructions, industrial area and vehicle as well, they confuse about the quality of rainwater
Therefore, rainwater now is applied only for non-potable purpose The RWH system in this house was constructed ten years ago This RWH system was chosen for examination of rainwater purification
The system design follows traditional RWH systems in Red River delta without any manual from any sector The system contains 56 m 2 of ceramic roof as collecting area, 8m of plastic downspout connected to a large cement storage tank The tank size is 4.7m long, 1.5m wide and 1.8m high The real storage capacity is 12.3m 3
To promote the application of water treatment and disinfection methods, two different scenarios of rainwater treatment were applied The first one is commercial filter including RO in combination with UV lamp The second method is using UV lamp dipped in rainwater barrel Water obtained after each method is collected regularly and then checked the quality to compare the efficiency of two methods The detail
Figure 3.2 Pictures of the pilot of rainwater harvesting system (a: Catchment roof, b: Storage tank) information of each method and experiment conducted are represented in the following part
3.3.2 Commercial filter containing RO in combination with UV lamp Installed devices and system
The commercial purifier employed in this examination is DEWX RO AQUAPRO Serise AP-60 supplied by DEWX Vietnam, Hanoi The design process water volume is 60L/hour with 30 to 60% of recovery rate (varies with raw water quality) The components of the system presented in the above scheme are listed in Table 3.1
Figure 3.3 Design of DEWX RO AQUAPRO Serise AP-60 supplied by DEWX Vietnam
Table 3.1 Components of DEWX RO AQUAPRO Serise AP-60 supplied by DEWX Vietnam
1 The program 20”5 PP SPUN FILBER CARTRIDGE
2 Activated Carbon 20”10 ACID WASHER CARBON
3 RO Film Mode RO ELEMENT NSF 100G x 4 pieces
4 Subsequent activated carbon TASTE & O FILTER
The working mechanism of the purifier and function of each component are explained in detail in Chapter 2
To improve the working efficiency of the system, an UV lamp (is connected after the system and before the output point The commercial flow type UV water sterilizer module with TUV T5 mercury lamp (16W, 345mm) of wavelength 254 nm was used
The storage capacity of the lamp module was 750mL and retention time was 1.8 minutes according to our calculation
The water purifier system was operated 1-3 times a week by pumping up rainwater from the storage tank to the system from December 2018 to May 2019 26 batches of sample were collected To observe the performance of the system, 4 samples of water were taken after 30 minutes running as follows
(1) Raw water: Water taken from the storage tank
(2) Post RO water: Water flow through the RO purifier, before coming inside the UV lamp
(3) Concentrated water: discharged water come out of the RO purifier
(4) Treated water: Water come out of the UV lamp and before storage
Figure 3.4 Sampling scheme of the examination of RO purifier in combination with
These 4 samples are collected into sterilized bottles and checked quality in the laboratory of Master program in Environmental Engineering, Vietnam Japan University except temperature and dissolved oxygen (DO) that were measured on-site
The checked parameters are in both physiochemical and microbiological aspects The detail experiments are given in 3.3.4
Another scenario was conducted to increase the quality of harvested rainwater, which is UV lamp dipped in water barrel The commercial UV submersible water sterilizer module Series GWT-15 with T515 mercury lamp (15W, 315mm) of wavelength 254 nm (Wonder) was used
In this scenario, raw water is transferred from cement storage tank into 100L plastic tank Toward the stable observation, the amount under UV sterilization in the barrel was kept at 60L for every experiment Samples are collected from beginning of March
2019 to the end of May 2019 There are 6 batches of sample collected
Figure 3.5 Examination system of submerged UV sterilizer
Water samples were collected at various time intervals:
(1) Raw water: water taken from plastic barrel
(2) 20s water: water after 20s under UV-irradiation
(3) 1 minutes water: water after 1 minutes under UV-irradiation
(4) 2 minutes water: water after 2 minutes under UV-irradiation
(5) 5 minutes water: water after 5 minutes under UV-irradiation
(6) 7 minutes water: water after 7 minutes under UV-irradiation
(7) 10 minutes water: water after 10 minutes under UV-irradiation
These 7 samples of water were collected every week into sterilized bottles and checked quality in the laboratory of Master program in Environmental Engineering, Vietnam Japan University The checked parameters are in both physiochemical and microbiological aspect The detail experiments are given in 3.3.4
3.3.4 Measurement of physicochemical quality Physicochemical quality measurement
The water samples were conducted in measurement including pH, conductivity, turbidity and dissolved oxygen Water temperature, DO and conductivity was measured by portable multi meter HQ-40d (HACH) pH was measured by pH meter (METTLER TOLEDO) Turbidity was measured by using TN-100 (Thermo)
3.3.5 Measurement of microbiological quality Total Coliforms and E.coli measurement
In this study, Total Coliform and E.coli are chosen as bacteriological quality for rainwater Membrane filter procedure is employed to measure the concentration of Total Coliform and E.coli in all samples This method introduces a direct count of
Total Coliforms and E.coli in water sample, especially water with low level of suspended solid, sludge and sediment A cellulose acetate membrane with pore size of 0.45àm was used to filter measured volume of sample under vacuum After filtering, bacteria are concentrated on the membrane surface and then cultivated on sterile medium in sterile petri dish and kept in incubator at an appropriate temperature for suitable time Whether coliforms including E.coli exit in checked sample, colonies formed can be directly counted Depend on the quantity and quality of water to be checked, suitable dilute ratio should be applied in sterile diluent toward the best observation (Balance and Bartram, 2002)
Results and discussion
Web survey of rainwater harvesting manuals in the world
Therein, 52% of the manuals are instruction for developed countries group, meanwhile 48% of the manuals are from the group of developing countries The detail results of each categories of analysis are presented in the following parts
The purpose of using rainwater is divide into three purposes including potable use, non-potable use and both potable and non-potable The results exhibited in Figure 4.1 show that 64% of the collected manuals recommend people using rainwater for both potable and non-potable purpose Meanwhile only 11% of manual encourage the use of rainwater for drinking In addition, there is 25% of the manuals warning that this type of water is only suitable for non-potable purpose for example gardening, washing cloth and cleaning house
It is an extremely considerable point is that in developed countries group, around 50% of the instruction recommend that rainwater should be only used in non-potable purpose and none of them recommend household family to use rainwater for drinking
Nevertheless, there is no manual in developing countries group prevents people from drinking rainwater, especially 25% of them encourage the use of rainwater for drinking
The results are reasonable based on the difference between the living standard of developing countries and developed countries In developing countries group, the availability of improved sources of water such as clean water supply or bottle water is lower than in the developed countries, therefore the use of drinking rainwater is encouraged Literally, the popular in drinking use of rainwater require more strict water treatment especially disinfection However, this aspect will be discussed in the following parts
4.1.2 Structure and materials for rainwater catchment roof
Figure 4.2 Different structure of roof
Regarding the design of the catchment roof, there are two types of the roof structure are discussed in this study which are sloped roof and flat roof The result is shown in Figure 4.2 Materials of the roof are also considered in the study In addition, the comparison between materials for roof in developing countries and developed countries are also compared They are shown in Figure 4.3
Figure 4.1 Purpose of using rainwater (a: Total;b: Developing countries, c:
Developing countries potable both non-potable
Figure 4.3 Materias for roof (a: Total; b: Developing countries; c: Developed countries)
According to the harvested result in Figure 4.2., 73% manuals encourage the construction of the roof with slope design and the only some manuals encourages the construction of the flat one The roof slope affects to the runoff during a rain event A steep roof design leads to quicker runoff then results in higher catching performance
In addition the steep roof can be easier to be cleaned than the flat one A flat roof causes the water to more slow movement of water, therefore increases the contamination risk on the catchment surface For these reasons, sloped roof design is highly recommended
Regarding the roof materials, there are six types of considered material in this study: metal including every metal, alloy and galvanized metal; wood; concrete including different types of concrete, cement and brick; synthesized material with high technology in manufacture; green roof which is covered by grass of plants toward green building design According to Figures 4.3.b and 4.3.c, metal is now considered as the most popular material for roof over the world which counts for 33% in both two groups of countries In the developing countries, concrete take the equal role to metal and followed by synthesized material and green roof at the same level of 17% without any trace of wood There is an interesting difference that in the group of developed countries, at the second level of popular material is wood, there is also no exist of
Metal Wood Concrete Synthesized material Green roof
(c) green roof The popular of wood material in developed countries but not in developing countries can be explained based on the cost of construction and maintenance of this type of roof, the use of wood requires better material for covering to make sure that they can suffer from the rain and sunshine
4.1.3 Design and material for gutter
The results for shape and materials of the gutter system are shown in Figure 4.4 There are three popular shapes of the gutter in RWH system Half-round shape is the most favorite choice because of the easy installation and maintenance as well as the higher ability to avoid the attachment of dirt, debris and microorganism
On the aspect of material, materials such as metal, Polyvinyl Chloride and wood or bamboo are the best options In the world, PVC still takes an outstanding role in the field of material and in gutter material as well Metal is also considerable
Figures 4.5.b and 4.5.c show an interesting different in gutter materials between two groups of countries, that is the existence of wood and bamboo as gutter material used in developing countries meanwhile in developed countries there is no manual mentioning about it It can be easily explained that bamboo or small tree are easy to find and cheaper than other material, cost benefit is an important point need to be concerned in developing countries
4.1.4 Installation type and material for storage tank
In this part of the study, two aspects regarding the installation types of storage tank including underground and aboveground and materials for tank including concrete, metal, wood and synthesized materials
Figures 4.6.a and 4.6.b display a significant difference in the design of tank between manuals for two groups of countries Meanwhile 57% of the manuals in the developing group recommend people to construct the above ground tank, more than 70% of the manuals in developed group said that it has better to build the underground tank, especially 9% of them highly recommends this type of tank The attributed reason for this difference is the lower in development of developing group in comparison to the developed group in both technology and economic Toward the construction of underground tanks, higher cost and technology are required that families living in developing countries seem hard to afford
Figure 4.5 Material for gutter (a: Total; b: Developing countries; c: Developed countries)
Regarding the materials for the tank, materials for tank in two groups follow the same trend according to Figure 4.7.a and 4.7.b Concrete is considered as the most popular material for tank followed by synthesized material, metal and wood
Figure 4.6 Type of tank ( a: Developing countries; b: Developed countries)
Figure 4.7 Materials for tank (a: Developing countries; b: Developed countries)
Above ground Underground Both types
Material for tank in developing countries Concrete Synthesized materials Metal Wood
Questionnaire survey of rainwater harvesting situations and people’s attitude
The number of family member was mainly between 4 and 6 as shown in Figure 4.10
This number is a little larger than that in urban area of Hanoi and typical family population in this peri-urban area today
Figure 4.10 Number of family member
4.2.1 Overlook of current situation in the area of study
In the first questions of the questionnaires, the realistic of using different water sources in the area as well as the cost of supply water each family has to pay every month is considered
Figure 4.11 Types of water used
Water supply Ground water Rainwater
According to the collected surveys, there are three main sources of water used in Yen Nghia commune, Ha Dong district, Hanoi city which are water supplied from water treatment plants, groundwater and rooftop harvested rainwater as shown in Figure 4.11
Wherein, water supply stands for the largest percentage of total water sources at 59% followed by rainwater at 23% and groundwater at 18% Figure 4.12 indicates the types of water used in each family through the percentage of families use each type of water
Based on the figure, around 50% of asked families use only water supply because of its convenience access 18% of asked households use rainwater as the second source along water supply and around 16% use all the three types of water In some case people use only groundwater and rainwater without any water supply but with very low percentage of 4% There is no family use only rainwater or groundwater because of the limitation in quality and quantity of these water sources
Figure 4.12 Percentage of families use each type of water
Among these three sources of water, only water supply requires monthly payment
Figure 4.13 gives a brief look at the monthly water bill of family using supplied water in the area Half of the surveyed families have to pay from 100.000 VNĐ to 200.000
Supply water only ground water onlyRainwater only Supply water and ground waterSupply water and rainwater Ground water and rainwaterThree types
VNĐ each month for water use In the range of this study, no questionnaire about the income of each family was taken, therefore we cannot make a comparison between the water bill and income so far However, we are looking forward to the reduction of water bill by encourage the use of harvested rainwater in this area
Purposes of using rainwater in this area are illustrated in Figure 4.14 with three categorizes of potable, non-potable and both types purposes The largest amount of families only use rainwater for non-potable purpose, locating the second position is purpose of both potable and non-potable Meanwhile, only 16% of asked family answered that they use this type of water for drinking purpose The attributed reason for this situation is that the lack of confidence in the quality of rainwater
Regarding the water treatment methods used in this area, Figure 4.15 shows a real situation Beside 4% of families do not use any treatment method and 2% use other methods of treatment, our research pays attention of two kinds of treatment methods which we are also considering the performance on rainwater treatment, commercial types including RO purifier and UV irradiation According to the results, 90% of the currently applied methods is commercial purifier, it illustrates the ability to afford to our further introduced system About UV irradiation, only 4% of households use this
Less than 50.000 VNĐ 50.000 VNĐ to 100.000 VNĐ100.000VNĐ to 200.000 VNĐ more than 200.000 VNĐ type of treatment which motivates our study to improve the use of UV lamp in rainwater treatment Purpose of using rainwater was also asked in the questionnaire
Figure 4.14 Purpose of using rainwater
An additional question was given to survey the current employed water treatment methods
Figure 4.15 Types of water treatment 4.2.2 Willingness to use our introduced rainwater treatment systems
Questions regarding to the willingness of people in the area to pay for introduced systems including RO purifier, combination system between RO purifier and UV lamp as well as the submersible UV lamp toward the drinking quality of rainwater were also taken in the study
No Commercial filter UV Other
Based on the results shown in Figure 4.16.a, 4.16.b and 4.16.c, totally, most of the asked families agree to pay for introduced system For the question of the willingness to use a filter system with RO purifier which costs around 4.000.000 VNĐ, 84% of households gave the “yes” answer For the question of willingness to use combine systems between RO purifier and UV lamp with the cost of 4.700.000 VNĐ, around 60% families agreed to pay In addition, the question about the willingness to pay for submersible UV lamp gained 62% of agreement The observed positive results suggest the extremely reliable of our study on application of two rainwater treatment methods including combine systems of RO and UV and submerged UV lamp scenarios
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))
Examination of rainwater purification in a typical existing RWH
To better access of the employed methods performance, rainwater storage in the existing cement tank was checked quality in both physicochemical properties and microbiological properties
Table 4.1 indicates the measured parameters (median and range) of Raw water sample (rainwater) and the comparison to Vietnam standard and WHO standard for drinking water (WHO, 2011; National Technical Regulation on Domestic water quality)
Based on the data given in Table 4.1, the physicochemical quality (Conductivity, pH and Turbidity) of Raw water is almost affordable for drinking purpose according to both National Vietnam standard and WHO standard for drinking water However, the microbiological quality in concentration of Total Coliforms as well as E coli is higher than the standard of non-detection followed the both standards
Table 4.1 Quality of Raw water in storage tank
Parameters Raw water Vietnam standard*
Figure 4.17.a and 4.17.b display the oscillation of rainwater microbiological quality in different sampling days The number of Total Coliforms fluctuates from some to several ten thousands CFU/100mL and number of E.coli is also fluctuates from some to several thousand CFU/100mL These concentrations showed same order of contaminations by Total Coliforms and E.coli as a survey in Hanoi reported by (Lee et al., 2017)
Possible explanations of this impressive fluctuation includes the accumulation of microorganisms, dust, leaves, bird droppings and other contaminants on the roof which can be washed by a rainfall and explain high concentration of microorganisms in the tanks
The measured number of Total Coliforms from the end of February to April seems higher than in the former time of sampling according to Figure 4.17.a It could be explained by the rainy season starting from beginning of March in the Northern area of Vietnam which causes stronger washer of roof contamination into the tanks then increase the microbiological risk
For a short conclusion, rainwater harvested from rooftop in the area cannot be used directly for drinking because of their pathogenic risk indicated by Total Coliforms and
E.coli abundance Further treatment methods are required toward the potable purpose as proposed by (Lee et al., 2017)
4.3.2 Combination system of RO purifier and UV sterilizer Physicochemical properties
Physicochemical properties of water samples (mean and standard deviation) including pH, conductivity, turbidity, and dissolved oxygen are shown in Figure 4.18 to 4.21
Regarding the change in pH of water through the system, the trend can be observed pH of Raw water and Post RO decrease significantly (p=3.47E -10