Abstract

Since 2014, a well-designed rainwater for drinking (RFD) project has been successfully operating at Cukhe Elementary School, near Hanoi, Vietnam. During that time, daily rainfall data, water consumption, water quality and questionnaires to the community were prepared. Several concerns over the design and operation of RFD projects, such as lack of sufficient rainfall data, water quality concerns, and public acceptance, are identified and overcome. Modeled results from using observed daily rainfall data, and using a simplified method from insufficient monthly data, are compared. The simplified method using insufficient rainfall data is acceptable for design within the error range of 0–11%. Rainwater quality after the use of the point of use treatment device proved that a well-designed rainwater harvesting (RWH) system ensures safe drinking water, which complies with WHO and Vietnam drinking water quality standards (VDWQS) guidelines. The people of the community liked the RFD system because of the satisfactory water quality and the economic benefits of not needing to purchase bottled water. The success of the RFD project at the Cukhe Elementary School proved the potential of promoting rainwater as drinking water in rural areas in developing countries, where a safe drinking water supply is a challenge, and should be promoted as an important means to achieve Sustainable Development Goal 6.

INTRODUCTION

A safe and affordable drinking water supply, which is one of the targets in Sustainable Development Goal 6 (SDG6), is essential for life. However, millions of people around the world still do not have access to this necessity. In rural areas in particular, drinking water problems are more common due to governments' inability to establish centralized water supplies, and the lack of a low cost and sustainable water treatment approach.

Community-based rainwater harvesting (CB-RWH) is recommended as a promising solution to the drinking-water challenges in developing countries (Kim et al. 2016). RWH has been considered to be a sustainable method to obtain good-quality drinking water at a low cost and with little energy expenditure (Helmreich & Horn 2009; Ahmed et al. 2011; Nguyen et al. 2013). CB-RWH is considered to be adequate for most rural areas, as centralized water supply systems are often unaffordable given the remote locations and lack of financial resources (Peter-Varbanets et al. 2009).

However, common concerns of rainwater for drinking (RFD) projects are (1) a lack of sufficient rainfall data in remote areas to design the system, (2) uncertainty of water quality and (3) uncertainty of public acceptance. Obtaining detailed and suitable rainfall data in order to design a good RWH system is a challenge in remote areas, especially in developing countries. In RWH system performance prediction, the direct use of monthly rainfall data instead of daily rainfall data may lead to considerable errors (Zaag 2000; Thomas 2002; Imteaza et al. 2011). Most RWH systems in operation experience problems with water quality, which include turbidity with suspended solids, or sometimes insects easily observable with the naked eye. The poor quality of rainwater, however, is not inherent to the rainwater itself, but is caused mainly by the inadequate design or poor maintenance of the collection/treatment equipment (Dobrowsky et al. 2014). If rainwater is collected properly, it can be of good physical and chemical quality, but there are doubts over safety because biological contamination has been detected (Sazakli et al. 2007; Vialle et al. 2011; Gikas & Tsihrintzis 2012). This requires minimal treatment before use as drinking water (Amin & Han 2009a, 2009b, 2011). Further, public acceptance has been identified as a key factor for enhancing implementation and promotion of water management approaches (Sharp 2006). Clarification of the issues associated with user satisfactions to use RFD could facilitate production of better information and the targeted promotion of such systems. However, little is known about public attitudes towards and perceptions of RFD so far, particularly for Vietnam. There are several gaps in knowledge and understanding due to the lack of water quality and quantity information, the utilities of the system, and the outlook on economic benefits.

In July 2014, we installed a 12 m3 RWH system at Cukhe Elementary School, which is located in a rural area near Hanoi, Vietnam, and operated it to overcome these concerns. Several innovative technologies have been applied in implementing the Cukhe Elementary School RWHs. Local data were gathered by a simple rain gauge to compare the simplified method using monthly rainfall data and real data in the design for the RWHs. Measuring rainfall data and water consumption data is helpful for the democratic operation and self-control of RWH systems, as was suggested to be a good model for ‘governing of the commons’, proposed by Ostrum (1990), who later won the 2009 Nobel Prize in Economic Sciences.

This paper shows a successful case study of a RFD project at Cukhe Elementary School, overcoming the commonly encountered challenges, such as system modeling with insufficient rainfall data, water quality of the rainwater system, and public acceptance.

MATERIALS AND METHODS

Site description

Cukhe Elementary School is located in Cukhe, a remote village in the southern part of Hanoi, Vietnam (Figure 1). In the village, people do not have access to a safe water supply for many reasons. Firstly, the government cannot afford to establish centralized water supplies for this type of remote village. Secondly, river water, which was used for rural water supply, is no longer available because it has been polluted by recent urbanization and insufficient sewer systems. Finally, groundwater in this area is heavily contaminated by arsenic. The only safe drinking water is bottled water, which is too expensive for many village people to afford. The school, however, had to supply expensive bottled water for the young students, paid for by their parents. The school has 300 students, 15 teachers, and three buildings, with relatively secure and suitable roofs. The average annual rainfall is 1,680 mm.

Figure 1

(a) Location and (b) RFD system of Cukhe Elementary School, Vietnam.

Figure 1

(a) Location and (b) RFD system of Cukhe Elementary School, Vietnam.

Rainwater harvesting system

In July 2014, the Cukhe Elementary School rainwater harvesting system was installed as a corporate social responsibility (CSR) activity, donated by The Lotte Department Store, Korea. The system was designed and the construction was monitored by a team from Seoul National University and a non-governmental organization (NGO) named RainForAll. The construction was by local labor and used locally available materials in order to be technically independent, so that the operation and repair can be later performed by local people. Figure 2 is a schematic diagram of the Cukhe Elementary School RWH system. The rainwater was collected from the roof of one of the school buildings, which is made of galvanized iron roof material. Rainwater collected from the roof is followed by a 120 L first flush diverter, which is installed to prevent most of the deposits from entering the rainwater storage tanks. Rainwater is stored in two separate 6 m3 stainless steel tanks to enhance the sedimentation capacity. In the storage tank a simple ‘J’-shaped pipe, called a calm-inlet, was installed to avoid the resuspension of bottom sludge. The sludge deposited at the bottom was drained manually by the decision of the operator, who opened the drain pipe until clear water drained. To ensure rainwater quality for safe drinking, a simple UV filter was installed near the tap to treat microorganisms. Here, water level gauges and water meters were installed to monitor remaining water supplies and cumulative water consumption.

Figure 2

Schematic of the rainwater tank at Cukhe Primary School in Vietnam.

Figure 2

Schematic of the rainwater tank at Cukhe Primary School in Vietnam.

Analysis of operational data

The design of a rainwater harvesting system is usually done by a simple mass balance equation using daily rainfall data and water consumption. However, the lack of daily rainfall data was an issue for a remote rural area, because rainfall data are primarily collected in urban centers. Therefore, Cukhe Village did not have adequate rainfall data to make a precise RWH design. The solution was to install a simple rainfall gauge and to work with a student science group to maintain rainfall records via a website (Figure 3). This rain gauge has the same design as first developed in AD 1441 by King Sejong the Great of the Joseon Dynasty, which is old Korea (Han & Park 2009). Daily rainfall data were measured with the rain gauge from February to December 2015. Furthermore, rainwater supply was monitored by a water meter for 1 year in 2015. In this paper, the collected data are used to evaluate RWH system performance and compare with the simplified method using monthly rainfall data (Nguyen 2016).

Figure 3

Rain gauge installed at Cukhe Primary School in Vietnam (Kim et al. 2016).

Figure 3

Rain gauge installed at Cukhe Primary School in Vietnam (Kim et al. 2016).

Rainwater quality was also checked. Rainwater samples were collected five times from a tap directly connected to the storage to measure stored rainwater quality, and collected twice from the other tap after treatment. Stored rainwater sampling was carried out in September, October and November 2014, and March and June 2015. Treated water sampling was carried out in January and October 2015. The following parameters were analyzed for each sample of rainwater collected: pH, total dissolved solids, turbidity, nitrate, nitrite, ammonia, hardness, arsenic, iron, cadmium, nickel, chromium, manganese, mercury, selenium, lead, zinc, Escherichia coli, and total coliforms. All analyses were carried out following Standard Methods (APHA, AWWA, WEF 1995).

Public acceptance interview

To investigate the public acceptance of the RFD project in Cukhe Elementary School, a total of 188 stakeholders, including teachers, students and their parents, who used the RDF system, were interviewed with the same questions about their satisfaction. The questionnaires covered the reliability of the rainwater quality and quantity, their satisfaction with the operation, and maintenance of the system. Finally, their satisfaction with the economic benefits of the project was examined.

RESULTS AND DISCUSSION

Verification of the model with operational data

A mass balance model to predict the performance of a rainwater harvesting system needs daily rainfall data and daily water consumption as an input. From the simulation, the design and operation parameters, such as annual water savings (WS), number of no water days (NWD) and rainwater utilization efficiency (RUE), were calculated for different tank volumes. Nguyen (2016) suggested a simplified method, using only the monthly data for design. Fortunately, daily rainfall data at the school were collected by the students after the installation. To verify the simplified method, these data were used in the simulation and compared.

After installation, the school used 59.7 m3 of water for 1 year. Assuming consistent usage, the average daily demand is 0.55 LPCD (liter per capita per day). According to an interview with the principal of the school, there had been no empty day of the storage since installation. This suggests that the RWH system has satisfied all drinking water demand. Before installing the system, students had to pay US$0.45 (VND 10,000) per day for the equivalent of 0.53 L of bottled water.

Daily rainfall was measured by the rain gauge and recorded by students. Figure 4 shows recorded daily rainfall from February to December 2015. Most rainfall was concentrated in the summer.

Figure 4

Recorded daily rainfall data in Cukhe Elementary School, February–December 2015.

Figure 4

Recorded daily rainfall data in Cukhe Elementary School, February–December 2015.

A benefit of local data collection is that it can result in a democratic decision of operation that can be used as a reference for the design and operation of an RWH system. Figure 5 compares the RWH performance by employing the actual recorded daily rainfall and the modeled rainfall generated from the limited rainfall data model. For the small tank sizes, there is a small error within 11%, introduced by using the modeled rainfall data instead of actual recorded daily rainfall data. At larger tank sizes, the model is closer and more similar to the results that used actual recorded daily rainfall data for the Cukhe Elementary School RWH system (12 m3 tank volume). These results prove the accuracy of the limited rainfall data model to design RWHs where there is lack of rainfall data.

Figure 5

Variation of (a) annual water saving, (b) number of no-water-days (NWD) and (c) rainwater utilization efficiency (RUE) using actual daily rainfall data and the modeled rainfall data as the input.

Figure 5

Variation of (a) annual water saving, (b) number of no-water-days (NWD) and (c) rainwater utilization efficiency (RUE) using actual daily rainfall data and the modeled rainfall data as the input.

Water quality

Table 1 shows the rainwater quality. As shown in the table, all chemical and physical parameters are much lower than Vietnam drinking water quality standards (VDWQS) and WHO standards over the year. Similar results can be achieved in other well-designed RWH systems. Rainwater has potential for microbiological contamination due to pollutants from bird and animal feces, dust and leaves. Table 1 shows a large variation of coliforms of 0–78,000 MPN/100 mL and E. coli of 0–3,200 MPN/100 mL in stored rainwater. Even though probabilities of illness caused by drinking microbiologically contaminated rainwater are very low and there is no link between untreated rainwater consumption and illness (Australian Government Department of Health 2011), disinfection prior to consumption is still highly recommended because of potential hazards.

Table 1

Stored rainwater and treated rainwater quality

Variables VDWQS WHO Stored rainwater Treated rainwater 
pH 6.5–8.5 – 6.3–7.9 6.36–7.24 
TDS (mg/L) 1,000 – 26–53.8 23–47.6 
Turbidity (NTU) – 0.05–1.2 0.6 
Hardness (mgCaCO3/L) 300 – 5–22 10–13 
Nitrite (mg/L) 0.22–2.31 0.006–0.11 
Nitrate (mg/L) 50 50 0.25–4.1 1.3–2.0 
Ammoniac (mg/L) – 0.09–0.86 0.03–0.2 
Sulfate (mg/L) 250 – <1 0–1 
Hydrogen sulfide (mg/L) 0.05 – 0.025–0.035 0.03–0.035 
Chloride (mg/L) 300 – 0.05–0.2 0–0.1 
Arsenic (mg/L) 0.01 0.01 <0.005 0–0.005 
Iron (mg/L) 0.3 – 0.025–0.084 0.05 
Cadmium (mg/L) 0.003 0.003 <0.0002 0–0.0002 
Nickel (mg/L) 0.02 0.07 <0.001 0–0.001 
Chromium (mg/L) 0.05 0.05 <0.001 0–0.001 
Manganese (mg/L) 0.3 0.4 <0.035 0–0.035 
Mercury (mg/L) 0.001 0.006 <0.0002 0–0.0002 
Selenium (mg/L) 0.01 0.01 <0.0002 0–0.0002 
Lead (mg/L) 0.01 0.01 <0.001 0–0.001 
Zinc (mg/L) – 0.046–0.05 0.01 
Aluminium (mg/L) 0.2 0.2 <0.001 0–0.001 
Total coliform (MPN/100 mL) 0–78,000 
E. coli (MPN/100 mL) 0–3,200 
Variables VDWQS WHO Stored rainwater Treated rainwater 
pH 6.5–8.5 – 6.3–7.9 6.36–7.24 
TDS (mg/L) 1,000 – 26–53.8 23–47.6 
Turbidity (NTU) – 0.05–1.2 0.6 
Hardness (mgCaCO3/L) 300 – 5–22 10–13 
Nitrite (mg/L) 0.22–2.31 0.006–0.11 
Nitrate (mg/L) 50 50 0.25–4.1 1.3–2.0 
Ammoniac (mg/L) – 0.09–0.86 0.03–0.2 
Sulfate (mg/L) 250 – <1 0–1 
Hydrogen sulfide (mg/L) 0.05 – 0.025–0.035 0.03–0.035 
Chloride (mg/L) 300 – 0.05–0.2 0–0.1 
Arsenic (mg/L) 0.01 0.01 <0.005 0–0.005 
Iron (mg/L) 0.3 – 0.025–0.084 0.05 
Cadmium (mg/L) 0.003 0.003 <0.0002 0–0.0002 
Nickel (mg/L) 0.02 0.07 <0.001 0–0.001 
Chromium (mg/L) 0.05 0.05 <0.001 0–0.001 
Manganese (mg/L) 0.3 0.4 <0.035 0–0.035 
Mercury (mg/L) 0.001 0.006 <0.0002 0–0.0002 
Selenium (mg/L) 0.01 0.01 <0.0002 0–0.0002 
Lead (mg/L) 0.01 0.01 <0.001 0–0.001 
Zinc (mg/L) – 0.046–0.05 0.01 
Aluminium (mg/L) 0.2 0.2 <0.001 0–0.001 
Total coliform (MPN/100 mL) 0–78,000 
E. coli (MPN/100 mL) 0–3,200 

At the point of use (POU) after filtration, all the parameters including both total coliforms and E. coli parameters satisfy VDWQS and WHO, confirming that the UV filtered water was safe enough to drink. In rural areas in developing countries, a UV filter is recommended to eliminate microbiological contamination from rainwater because of its long duration and low cost. These results prove that RWH can safely be used for drinking with a POU treatment system.

Public acceptance

Table 2 shows the opinions of the teachers, students and their parents about the RFD system in Cukhe Elementary School. Through the surveys and the interviews, it was shown that the community has a positive perception of the RFD project. They consider rainwater to be a safe and clean source of drinking water. Furthermore, they also showed high satisfaction with the RFD project's economic benefits, which were proved to prevent the purchase of costly bottled water.

Table 2

Stakeholders' opinions about the RFD project at Cukhe Elementary School

  Very disappointed (%) Disappointed (%) Normal (%) Good (%) Very good (%) 
Are you satisfied with the taste of rainwater? 51 35 
Are you satisfied with the rainwater quality? 41 42 11 
Do you think the RDF system supplies enough water? 39 39 12 
Do you think the RDF is convenient for use? 45 41 11 
Do you think the system is economic? 36 35 26 
  Very disappointed (%) Disappointed (%) Normal (%) Good (%) Very good (%) 
Are you satisfied with the taste of rainwater? 51 35 
Are you satisfied with the rainwater quality? 41 42 11 
Do you think the RDF system supplies enough water? 39 39 12 
Do you think the RDF is convenient for use? 45 41 11 
Do you think the system is economic? 36 35 26 

The public acceptance and success of the RFD project at the Cukhe Elementary School can be widely transferred to their communities and villages, since many of the stakeholders were involved in the RFD project. This may hopefully suggest the promotion and replication potential of RFD to achieve resilient and sustainable drinking water supplies in rural areas in developing countries facing water shortages, and should be promoted as an important means to achieve SDG6.

CONCLUSIONS

A well-designed RFD project has been in operation at Cukhe Elementary School in a rural area in Vietnam, a developing country, since June 2014. By monitoring rainfall data and water consumption, a community can democratically self-regulate water consumption and the data can be used for future designs.

It was possible to design a suitable system with a simplified method using monthly rainfall data. A well-designed RFD system ensures a relatively safe water source with good physicochemical quality. After applying POU treatment, it provides safe drinking water that is within the WHO and VDWQS guidelines.

Public acceptance of the RFD project was analyzed. The results suggested that CB-RWM has potential to achieve a resilient and sustainable water supply for drinking.

The success of the Cukhe Elementary School RFD project proved the potential for promoting rainwater as drinking water in rural areas in developing countries, where a safe drinking water supply is a challenge, and can shed light on a method to achieve equal access to safe and affordable water for all, which is suggested by SDG6.

ACKNOWLEDGEMENT

This research was supported by ‘Development of Nano-Micro Bubble Dual System for Restoration of Self-purification and Sustainable Management in lake’ project funded by the Republic of Korea Ministry of Environment; Institute of Construction and Environmental Engineering at Seoul National University; and Vietnam National University Ho Chi Minh City (VNU-HCM) under grant number C2017-48-03. Dao Anh Dzung and Duc Canh Nguyen are co-first authors of this paper. The authors wish to express their gratitude for the support.

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