At present, the novel coronavirus (COVID-19) outbreak (first spread in Wuhan, China in late 2019) has resulted in a worldwide severe pandemic that has already disrupted human life and civilization. This coronavirus has already caused a huge number of deaths and becomes a major threat for mostly older people who are suffering from diabetes, cardiovascular disease, cancer, and chronic respiratory syndrome [23]. The world's leading scientists, chemists, microbiologists, engineers, doctors, and other health professionals are working very hard to find proper solutions for this new virus by understanding the nature of COVID-19. There are many predictions available online nowadays about the microstructural properties and weather- and region-dependent nature of COVID-19; however, getting an active vaccine against this virus requires a significant amount of research effort together with on-going worldwide clinical trials. The world is seeking new hope while currently relying on the precautions that have been recommended by the World Health Organization (WHO), including social and physical distancing to control the rapid spread of this virus [24]. The outbreak of COVID-19 has overturned not only human life but also the global economy by seriously affecting all kinds of industries including food, agriculture, readymade garments, leather, building and infrastructure materials, energy and power sectors, science and technology and others all over the world [25–30]. Many industries and businesses were forced to take actions like job cuts, even in some cases shut down completely. As a result, millions previously in the workforce have become jobless, and severely affecting—directly and indirectly—developing countries like Bangladesh. As COVID-19 can transfer easily from one affected person to others (i.e., community transmission), it becomes a great concern how, as well as how long is needed, to get back to normal life. According to the proposal jointly made by WHO and FAO for food safety including multi-agency co-operation, proper inspections in different stages of production can mitigate significantly the spread of this corona-virus but to achieve this is a very much challenging task [31,32]. In these circumstances, the risk of contamination can be minimized and kept under control only if the local demand for foods and protein supply can be met by the local growers and suppliers. In Bangladesh, the well-being of the economic cycle as well as of a large number of the population is mainly dependent on good agricultural and industrial prospects. All agricultural and industrial sectors including garment, leather and industries requiring construction materials are major candidates where continuous electricity supply is needed for maintaining a non-disruptive production cycle for the well-being of the economy. However, currently, these sectors are facing severe problems during the COVID-19 crisis and maintaining a continuous electricity supply will continue to be a major issue for many smallholder farmers in the rural farming and cultivation areas in post-COVID-19 Bangladesh [33–42]. Besides, the national grid electricity supply, solar photovoltaics (PVs)-assisted

power generation can help all industries and factories to maintain their continuous production cycle. Therefore, designing new and modification of existing infrastructures that can generate and save energy will be the most effective approach for the well-being of post-COVID-19 Bangladesh and will assist in returning the country to a normal lifestyle. In addition, this energy engineering can be a model for future modern farming in any country of the world and, in the near future, potentially can help to diminish the current rise in unemployment due to the COVID-19 pandemic by making all the farms and food industries active and fully productive again.

In this article, we design and optimize a hybrid power generation system that can be applied together with thin-film, low-emissivity (Low-E) coating-assisted, energy-saving features for self-sustainable off-grid or semi-off-grid infrastructure for cattle farmers in rural areas. In Bangladesh, grid connection is not available throughout the country, and there is no alternative of a micro-grid to ensure the power availability to any new or existing infrastructures for farming and food storage. However, the implementation of modern scientific processes can increase the production levels by up to 50%, whereas if the conventional power sources are used, the fuel cost will have a negative impact on profit margins. The organization of this paper is as follows: Section 2 briefly describes the materials and methods, where we describe the types of farms targeted and ways of power optimization. Section 3 describes in detail the means of engineering of energy generation and savings including the components that are considered in this work. Section 4 presents the optimized simulation results, and Section 5 includes a short discussion based on the outcome of the hybrid energy engineering optimization, followed by a conclusion in Section 6.

#### **2. Materials and Methods**

#### *2.1. Types of Farm*

Figure 1 shows the images of mostly available (typical house type) infrastructure in Bangladesh for limited land size cattle farms together with the schematic diagram of a proposed cattle house containing hybrid power generation systems, in conjunction with energy-saving, thin-film-coated roof materials. A thin-film coating, mainly the low-E coating-assisted roof material, can filter daytime sun irradiation. The low-E-coated glass becomes a modern day building material towards the development of net-zero building infrastructures. Low-E coatings are designed to filter the visible spectrum whilst reflecting the infrared (IR) spectrum, thus reducing the heat entering the building [43–47]. Most of the commercially available low-E coatings are glass-based; however, several companies have developed low-E-type coatings on very thin polycarbonate (clear plastic substrate) materials that can be retrofitted to any transparent material, including glass or Perspex. In our proposed cattle house (Figure 1b), rather than a clear polycarbonate roof material, we are introducing a low-E-type coated semitransparent roof material which will allow only the visible light and thus will not only save lighting costs but also reduce the heat by reflecting the IR spectrum (which is mainly heat) during the day time. The effectiveness of thin-film coatings on energy savings is detailed in the Section 3.4.

In order to study the economic feasibility of energy engineering aspects, various types of cattle farms categorized by size, were considered such as small, medium and large farms holding the land size of 0.5 to 2.0, 2.1 to 5.0, and above 5.0 acres, respectively. However, the details information about the land size and the number maximum animals in one row or column are preciously provided in the following Refs. [48,49]. Table 1 presents the criteria for different types of the farm used in this study.

**Figure 1.** Images of a cattle farms. Existing typical cattle house in Bangladesh (**a**), and the schematic diagram of a proposed cattle house that contains hybrid power generation systems, together with energy-saving thin-film-coated roof materials (**b**).

#### *2.2. Optimization of a Power-Generating System*

We aimed to find a feasible and sustainable energy generating system that can meet the energy demand in cattle farming for the rural areas in Bangladesh. The PV systems are considered as the best renewable energy resources due to the great advantages that solar cells/module does not require any raw material to feed and have a very low operation and maintenance cost with a long-term operational life. However, the drawback for using solar cell is that it depends on sunlight and when sunlight is not available (such as a rainy and cloudy day or night) the energy extraction is greatly hampered. The PV module can be used only during the daytime with clear sky (i.e., a sunny day) thus confirms the unsuitability of use for the microgrid system. However, a storage device such as the battery can solve the problem by storing the unused excess power and fed to the load when it requires. Therefore, the PV-battery system can be a sustainable solution to meet the demand of a cattle farm. Techno-economic analyses for different energy (single generator, PV-Battery and PV-Generator-Battery hybrid) systems were carried out to find the most convenient and economically feasible microgrid system. Hybrid Optimization of Multiple Energy Resources (HOMER) software, developed by National Renewable Energy Limited (NREL, Boulder, CO, USA) is used to optimize the hybrid power systems. HOMER simulation tool allows comparing various types of systems in combination with capital, maintenance and other types with a given energy resource to meet the system load demand. Figure 2 shows the schematic diagram of HOMER algorithm that used in this work, where a sustainable power source is designed by considering PV cells, storage device, diesel generator, converter and other appropriate devices.

**Figure 2.** Schematic diagram of Hybrid Optimization ofMultiple Energy Resources (HOMER) algorithm.

In this module, the available renewable energy resources and load profile for the system are required to set as input. Besides this, for the cost calculation, the price and operational datasheet need to be supplied for PV, Battery, Converter, generator and other devices. The economic analysis performed using the HOMER software for different types of farms with the payback period and energy engineering are detailed in the next section.

#### **3. Engineering of Energy Generation and Savings**

#### *3.1. Design, Components and Optimization of Hybrid Power Generation System*

#### 3.1.1. Solar Radiation Data

The solar data available in HOMER pro software was used in this study which was originally extracted from the NASA surface meteorology and Solar energy database. The clearness index defines as the fraction of transmitted solar radiation through the atmosphere to the Earth surface is also an important parameter for HOMER Pro simulation tool. The clearness index is a dimensionless unit which varies from 0 to 1. For a clear sky, the index is close to 1 whereas close to zero for a dense cloud condition. The monthly solar radiation with a clearness index for Bangladesh is shown in Figure 3. It can be seen that the average daily solar radiation is maximum in April while the clearness index is maximum in December. It is because April is the summer when the sun is tilted to the northern hemisphere and at that time the sky becomes cloudy. On the other hand, in winter (December and January), the length of the day is comparatively shorter, and the sun is tilted to the southern hemisphere. However, at this time the sky is clear due to low humidity.

**Figure 3.** Monthly average solar radiation for a year.

#### 3.1.2. Load Consumption Analysis

Load consumption is the most important part of any power system. The load consumption profile indicates the variation of load demand in different time of the day, month and season. This profile completely depends on the nature of the system. Keown et al. [50] reported that if the temperature rises above 80 ◦F (26 ◦C), feed intake by the cattle reduced significantly and thus impacts their growth. Additionally, at 90 ◦F (32 ◦C) or above, the milk production reduces by at least 3 to 20%. Therefore, a convenient and comfortable atmosphere is necessary to maintain for the maximum production. For the medium and small farm energy is required only for lighting and ventilation, but for the large farm milk collection and storage device are considered as additional load along with lighting and ventilation system.

For a large cattle farm, the most challenging period is to collect a huge amount of milk and marketing it instantly. For this reason, a large cattle farm should have a milking parlor and refrigeration system. G. Todde et al. shows that the power rating of the vacuum pump for each milking cow is 75 W [51]. A cow has to go to the milking parlor twice a day and on an average, it takes 15–20 min for milking. Therefore, the daily power requirement for milk collection is given by,

$$75\text{ W} \times 20\text{ min} \times 2\text{ times} \times 100\text{ cows} / 1000 \times 60 = 5\text{ kVh}$$

On the other hand, the liquid milk leaves the cow at 38 ◦C and requires cooling at 4 ◦C to avoid milk spoil. To prevent the bacteria growth, the milk should maintain 38 to 10 ◦C during the first hour after collection and from 10 to 4.4 ◦C during the second hour [52,53]. Upton et al. [54] reveals that the consumed electricity for milk cooling system is 13.02 Wh/L. If we consider the daily average milk production per cow is 15 L, then the daily power consumption for refrigeration can be calculated as follows:

#### 15 L × 100 cows × 13.02 Wh/L/1000 × 24 = 0.81 kWh

Inside the cowshed, proper lighting and ventilation system required for a healthy environment for the cattle. In Bangladesh, the average temperature is 32 ◦C in summer. In this study, LED lights and ceiling fans are considered for lighting and ventilation system. Table 2 shows the power rating and appropriate combination for different types of the farm are given below.

**Table 2.** Power rating, the combination of lighting, and ventilation devices for different types of farm.

Figure 4 shows the differences in load consumption for three different types of farms, where it can be seen that the cattle farm load stays at the minimum stage in the winter season (November to February). This is because, in the winter season, the cooling system is not necessary for the farm. At night, there is hardly any load for the small- and medium-sized farm except lighting. On the other hand, the large farm has to switch on the refrigerator to store milk and, as a result, it requires a load consumption of more than 30 kW during the winter season. In March and October, the load demand is at a moderate stage. During this time, the temperature at night in such a state that the cooling system is not required for the cowshed. However, during the daytime, fans are needed to be switched on. At the summer season (April to September), there is a huge chance of heatstroke for the cows. In order to stabilize the production of milk, an additional 24 h cooling system needs to be implemented. This 24 h cooling system consisted of a ceiling fan is the major challenge to meet the demand for energy supply. During the summer season, the load demand is maximum for all types of farms due to ensure a congenial environment inside the shed.

**Figure 4.** Monthly load profile for different types of farm.

#### *3.2. System Components*

#### 3.2.1. Solar-PV Module

Polycrystalline silicon PV panels are considered to perform the simulation process in this study. Considering the relation between the orientation of the solar panels and PV output; the PV panels are considered to be placed with south facing and a slope of about 22 degrees with earth surface. In this case, the temperature effect of the solar cell is neglected. The estimated primary cost of PV module is \$USD 1720/kWh including transport and installation cost. The replacement cost of the module is \$USD 1720/kWh considering the lifetime of about 25 years.

#### 3.2.2. Battery

The battery is a commonly used storage device for electrical energy. We consider a 12 V Lead Acid-type battery for running the simulation optimization. The primary installation cost of this storage equipment is \$USD 300/battery, whereas the replacement cost is \$USD 3000/battery. The potential technical parameters for the battery are listed in Table 3.

**Table 3.** List of the technical parameters of the proposed battery.

#### 3.2.3. Converter

A converter is used to convert an electrical signal from alternating current (AC) to direct current (DC) or else vice-versa. A converter is a combination of inverter and rectifier. A PV module produces DC and diesel generator supply AC to serve AC load. Therefore, to synchronize these signals for charging along with supply to the load, a converter is prerequisite for a hybrid power system. The estimated primary installation cost of the converter is \$USD 300/kW and the replacement cost is \$USD 300/kW. Table 4 presents the summarized technical parameters for the inverter and rectifier module.

#### 3.2.4. Diesel Generator

A diesel generator is a conventional power source which converts the chemical energy of diesel into the electric energy. The initial capital cost of the generator is \$USD 500/kW with an operational and maintenance cost is \$USD 0.030/operational hour. The replacement cost of the diesel generator is \$USD 500/kWh. According to the present market value of Bangladesh, the fuel cost is assumed to be \$USD 0.77/L (BDT 65). Technical specification of the diesel generator is summarized in Table 5.

**Table 5.** Summarized technical specification of the diesel generator.

#### *3.3. Sensitivity Analysis*

A sensitivity variable is a combination of a set of variables for which the HOMER software simulates technical and economic analysis. The incident sunshine is not the same and it varies time to time and place to place from the average value. Again, the levelized cost of energy (LCOE) and net present cost (NPC) depend on load profile and project lifetime. For each sensitivity case, HOMER does search for the cost-effective (lowest cost) system in their respective search limit. In this system, the considered sensitive cases are enlisted in Table 6.

#### *3.4. Thin-Film Low-E-Type Coatings for Energy Savings*

Most of the low-E-type coatings are mainly structured in a sequence of Dielectric/Metal/Dielectric (DMD) type multilayer containing either single or multiple metal layers. The DMD types thin-film multilayers have been studied extensively due to their promising application potentials in various fields including transparent heat regulation (THR). There are some examples of various DMD structure designs and their fabrication technologies are reviewed and listed in Ref [55]. Figure 5 demonstrates the example of clear and semi-transparent polycarbonate roof materials (Figure 5a,b) together with the details explanation of solar radiation spectrum and optical properties of different types of low-E-type coatings (Figure 5c,d). It can be noticed that the polycarbonate roof sheets are, though, suitable for industrial and agricultural purposes; however, they are not capable to filter the solar IR radiation which is mainly heat. The transmission spectral response curves presented in Figure 5d confirms the possible rejection of the IR spectrum mostly over 90%. It is said that 43% of heat is accumulated by the IR spectrum of the sunlight, so by using low-E-type coatings nearly 38% of solar heat can be controlled.

**Figure 5.** Example of clear and semi-transparent polycarbonate roof materials (**a**,**b**), spectra of sunlight (**c**) and optical properties of different types of low-E-type coatings compare to that of clear polycarbonate roof materials (**d**).

From the spectral response and solar radiation filtering performance (Figure 6), it is very clear that the transparent polycarbonate roof material does not bock any IR spectral radiation of sunlight, while the commercially available low-E-type, thin-film coating and even randomly designed a double metal layer containing DMD type thin-film coating can significantly reduce the radiant heat transmission of sun's spectra into the internal space for any infrastructures. Nur-E-Alam et al., reported that only 29% of solar IR heat (in between 780 to 1700 nm spectral region) can pass through a single metallic nano-composite layer contained DMD type coated glass [55]. Figure 6a shows the standardized spectral power density distribution of solar irradiation (AM 1.5 G) while Figure 6b represents the power density of solar radiation of filtered (through the clear polycarbonate sheet and several thin-film coatings) transmission spectra.

**Figure 6.** Solar spectrum calculation results in terms of the filtered spectrum of clear polycarbonate roof material and couple low-E-type thin-film coatings.

Overall, features of thin-film coatings clearly indicate that thin-film-coated transparent or semitransparent construction materials (roof or sidewall) can be an additive to save energy for any type of infrastructures for sustainable green earth.

#### **4. Results**

In this study based on the volume of the farm, we categorize the cattle farms into three different types, such as small, medium and large. In order to investigate the economic feasibility among the farms, we compare the optimized economic parameters for each type which is optimized by the HOMER pro software. The optimized equipment combination and basic economic parameter for each corresponding farm types are summarized in Table 7.

**Table 7.** Optimize combination of PV, generator and battery for hybrid system.

Figure 7 presents the cost analysis for different types of farms with three different energy source systems. It can be seen that the capital cost increases for a three power source component contained (PV, generator and battery) hybrid system compared to the single component (i.e., generator only) power system and a double power source component (i.e., PV and generator) hybrid system. However, the total cost is low for a three-power-source component-contained (PV, generator and battery) hybrid system due to low fuel consumption. It indicates that fuel cost is drastically reduced for PV, generator

and battery hybrid system. Besides, this operation and maintenance cost is also low for this system due to reduced operation hour of the generator.

**Figure 7.** Cost analysis for different types of energy sources.

We have also noticed that the LOCE is smaller for the PV, generator and battery hybrid system compared to that of generator alone or PV and generator system. Comparison of LCOE for different types of farm based on the different combinations of power systems is plotted in Figure 8. The LOCE for generator only and PV and generator hybrid system are almost the same for the small- and medium-sized farms, but for the large farm, the LOCE for PV and generator system is low. On the other hand, the LOCE for PV, generator and battery hybrid system for a small farm is comparatively lower than that of the medium and large farm.

**Figure 8.** Comparison of the LCOE for different types of farm.

Figure 9 presents a glimpse of global solar radiation and possible output power that could be generated from the solar spectrum. Hourly variation of solar energy, as well as the output power from a solar cell (Figure 9a), states that the power generation from PV plate is directly proportional to the incident global radiation at a particular place. At noon, the global solar radiation is optimum and at that time the production of electricity from the PV cell is optimum as well. The foremost downside of the solar cell is that it can produce energy only at daytime and it reaches its peak for a very short time duration. During the night and a cloudy day, solar module spends its ideal time without producing any energy.

**Figure 9.** Hourly variation of solar energy as well as the output power from the solar cell (**a**), an hourly variation of the PV output and battery discharge ratio for an optimized system for the medium-sized farm (**b**), monthly variation of PV and generator output pattern for optimized power system for medium-sized farm (**c**), and monthly variation of load demand and excess electricity production for a medium-sized farm (**d**).

Since the solar cell periodically produces energy and it cannot be controlled manually, a storage device can increase the efficiency of the system. From Figure 9b, it is clear that, during the daytime, the power output from the solar cell is optimum and, at night, when the sun is not available, the battery unit fed power to the system as a power source. The storage device can do back up for all time respective to its capacity. As a result, a continuous power source can be ensured by the PV and battery arrangement. Figure 9c shows that there is no need to use the generator at the winter season i.e., during November to February of the year in Bangladesh. During this time, the power generation from the solar cell and battery backup are sufficient to fulfil the load demand. On the other hand, the power generation from the solar cell during July (which is a rainy month in Bangladesh) is minimum (Figure 9c) due to the cloudy sky and solar power is not available as a rainy day as well. However, the load consumption remains at the maximum stage. As a result, to meet the electricity demand, the generator must supply the maximum amount of electricity at the same time. Whilst Figure 9d shows that the PV, generator and battery system produced excess energy during the winter season. At that time, the load demand is minimum and the production of electricity from PV panel excess the load demand. However, from April to October the load demand is maximum and at that time the production of excess electricity is minimum.

Figure 10 represents the average load, solar radiation and project life dependent variation of the LCOE. It can be seen (Figure 10a) that the LCOE decreases for the increases in load consumption for all types of farm. In this study, the baseline load for small-, medium- and large-sized farms are 7.97, 21.24 and 75.8 kWh, respectively. This graph shows that if all other parameters are fixed when the projected load is lower than the baseline load demand then the LCOE increases with decrease in load. On the other hand, if the load demand increase from the baseline load demand, the LCOE decreases with the load. However, the line for below the baseline load is stiffer than the line for higher load. It means that if the load demands decrease, the LCOE increases abruptly. However, if the load demand increases, the LCOE decreases at a slower rate.

**Figure 10.** The relation between load and the LCOE for different types of the farm (**a**), a variation of LCOE with projected lifetime for PV, generator and battery hybrid system (**b**), and variation of LCOE with incident solar radiation for PV, generator and battery hybrid system (**c**).

It can be noticed that the LCOE decreases with an increase in project lifetime for all types of farm (Figure 10b). The PV panel is a sustainable energy source, and it can produce energy for a long time without major maintenance thus diminishes the capital cost significantly for a long-term project. The LCOE has a negative correlation with incident solar radiation. On the other hand, it can be seen (Figure 10c) that the LCOE decreases with the increase of incident solar radiation. When the incident solar energy is increasing, the PV output power is also increasing. Since solar energy is a renewable source and it has no fuel cost, the more contribution of PV power over generator will decrease the overall energy cost.

Figure 11 shows that difference of greenhouse gas (CO2) emission from the generator, and PV and generator type energy sources are negligible for the small and medium farm. However, they have an abrupt decrease in CO2 emissions for PV, generator and battery hybrid systems. On the other hand, for a large farm, greenhouse gas emissions reduce chronologically for the generator, PV and generator, and PV, generator and battery system. Finally, it can be concluded that based on the greenhouse gas emission, PV, generator and battery hybrid system is more feasible than any other two types of farms.

**Figure 11.** Carbon dioxide emission from different types of the farms for different energy sources.

#### **5. Discussion**

From the simulation results, we would like to state the following remarks about this study:

In addition, the energy demand per cow for the small and medium farm is almost the same; however, for large-scale cattle farming, nearly 25% extra energy is required, as shown in Figure 12. This is because of the automation of collecting and storing milk for trading some distance place. As a result, the energy consumption per cow increase and the LOCE increases. Since per capita energy consumption is big for the large scale farm due to storing milk, the small- and medium-scale cattle farming is feasible from the economic point of view where the production is only for the local market.

**Figure 12.** Load demand for a single cow depending on the farm size.

#### **6. Conclusions**

We demonstrated the design and optimization of hybrid power system together with the addition of thin-film, Low-E coating assisted power-saving feature for next-generation cultivation and farming system. From the obtained hybrid energy system optimization results, we found the energy payback period for small and medium farms are 4.7 and 4.6 years, respectively; however, if the farm size is larger, this payback period could be 3.5 years. Note that during the hybrid energy system simulation the advantage of thin-film Low-E-type coatings was not accounted for. In summary, we can comment that our study of energy engineering together with the advanced building material coatings will be the model for modern farming in any rural areas, and will help to reduce the carbon emission footprint for any other countries as well.

**Author Contributions:** Conceptualization, M.N.-E-A.; methodology M.N.-E-A., M.N.H.; software, M.N.-E-A., and M.N.H.; validation, M.N.-E-A., M.N.H., S.M.A., M.K.B., and N.D.; formal analysis, M.N.-E-A., M.N.H., S.M.A., and M.K.B.; investigation, M.N.-E-A., M.N.H.; resources, M.N.-E-A., and M.N.H.; data curation, M.N.-E-A., M.N.H., and M.K.B.; writing—original draft preparation, M.N.-E-A., and M.N.H.; writing—review and editing, M.N.-E-A., M.N.H., S.M.A., M.K.B., and N.D.; visualization, M.N.-E-A., M.N.H., S.M.A., and M.K.B.; supervision, M.N.-E-A.; project administration, M.N.-E-A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

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*Article*

## **Sanitation Sustainability Index: A Pilot Approach to Develop a Community-Based Indicator for Evaluating Sustainability of Sanitation Systems**

#### **Shervin Hashemi**

Institute for Environmental Research, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea<EMAIL_ADDRESS>
Received: 5 June 2020; Accepted: 25 August 2020; Published: 26 August 2020

**Abstract:** Evaluating the sustainability of sanitation systems is essential in achieving the sixth sustainable development goal. However, there are only limited number of available evaluation indexes, which are utilized to macroscopically determine a community's sanitation coverage. Consequently, an index is required, which can evaluate different sanitation options for a specific community. In this paper, the sanitation sustainability index (SSI) is suggested as an indicator for evaluating the sustainability of sanitation systems. The SSI has sub-indexes that consider the technical, social, and economic aspects of the sanitation system, and all the variables are dimensionless and heavily dependent on the current state of the community where the sanitation system is going to be implemented. The applicability of the SSI was demonstrated by evaluating the implementation of two onsite sanitation systems, including one septic tank system and one resource-oriented sanitation (ROS) system in South Korea. A sensitivity analysis defined the variables that have significant impact, and the statistical distribution of the SSI for both systems was forecasted. The results showed that for South Korea, which has a profound history of utilizing human waste as fertilizer, utilizing the resource-oriented sanitation system is more sustainable, although it has a lower social sub-index score compared to the septic tank system.

**Keywords:** resource-oriented sanitation; sanitation sustainability index; SDG6; sustainability assessment; sustainable development goals; sustainable sanitation

#### **1. Introduction**

According to UNICEF and WHO [1], the population that utilize safely managed sanitation services increased from 28% to 45% from 2000 up to 2017. Accordingly, 2.1 billion people gained access to at least basic sanitation services. Despite that, 2 billion people still have no access to safe and sustainable sanitation system, 673 million people are practicing open defecation, and 3 billion people still lack basic sanitation; consequently, the sanitation crisis remains a global concern.

The sixth sustainable development goal (SDG6) is designed to solve these global issues before the year 2030 [2]. The objective of SDG6-2 is to provide full coverage of adequate and sustainable sanitation for the entire population. Following this objective, innovative approaches have been applied on new disciplinary understandings of sanitation, to provide sustainable sanitation for low-income regions [3]. Recently, national-scaled programs have been conducted to improve the notion of equity in sanitation to end critical challenges like open defecation [4]. Meanwhile, there are several indicators and indexes that are defined to monitor or evaluate the progress [5–7]. One example is the water, sanitation, and hygiene (WaSH) performance index suggested by Cronk et al. [8], which can be utilized to compare the performances of countries in achieving universal water, sanitation, and hygiene. The elements of this index include water and sanitation access and equity.

The development of these indexes is essential in achieving SDG6, because they present a comparative view of the progress of each country towards SDG6. Additionally, these indexes are useful for undertaking general national-scaled decisions to further progress towards fulfilling SDG6.

In many cases, comparing two different countries based on such macroscopic indexes may be misleading, particularly when there is a notable difference between the human development indexes of those countries [9]. Nevertheless, the economic, social, and technical characteristics of each country are different. Determining an appropriate index, which is flexible, suitable for every community, and reliable for comparison of progress, is crucial. Consequently, the use of an index that is better suited to evaluate sanitation systems for the implementation in a specific community is a suitable approach, and the evaluation should be performed based on the current technical, social, and economic status of the community.

An index proposed by Lundin et al. [10], which evaluates the sustainability of sanitation systems included several technical considerations. However, waste recycling and utilization, along with social and economic indicators, were not considered in that index. Another comprehensive index was suggested by Iribarnegaray et al. [11], which assesses the sustainability of water and sanitation management systems. This index is useful, as it considers the majority of relevant issues of sustainability. However, by developing innovative sanitation systems which can recycle sanitary wastes to be utilized as resources (e.g., fertilizers), there is an emerging need for providing innovative indexes, which can consider the effect of ability for onsite waste recycling on the technical, economic, and social aspects of the community [5]. In particular, economic indicators are required to consider a broader range of issues influencing the cost and probable benefits of implementing sanitation systems in developing countries [12]. Moreover, the insufficient evaluation process for the applicability of an index through limited case studies and demonstration projects is another bottleneck on the way to finding an appropriate sustainability index.

To provide sustainable sanitation for a community, understanding the technical, economic, and social characteristics of the community is critical. Numerous technical approaches toward the provision of sustainable sanitation have been studied [13–17]. These approaches provide a range of options for sanitation, including onsite sanitation systems using water-saving toilets, septic tanks, and resource-oriented sanitation (ROS) systems [18–25]. Moreover, some studies compare different sanitation systems based on economic views [12,26]. Social approaches toward sustainable sanitation were also considered in multiple studies [27–31]. However, there is still a need for a reliable index that can be utilized to determine a suitable sanitation system for a community based on availability, accessibility, and sustainability.

In this paper, the sanitation sustainability index (SSI) is proposed to evaluate the sanitation systems for implementation in any community. The SSI indicates the technical, social, and economic aspects of the sanitation system. The applicability of this index is demonstrated by utilizing it to evaluate the implementation of one septic tank and one ROS system in South Korea.

#### **2. Materials and Methods**

#### *2.1. Definition of SSI*

Figure 1 presents the SSI structure, which contains technical, economic, and social sub-indexes. Each sub-index has specific dimensionless variables, having values ranging from 0 to 1, with 0.2 intervals, indicating very low, low, medium, high, and very high criteria for evaluating the sustainability of a sanitation system.

Technical and economic sub-indexes are analyzed by simple equations, containing a fraction. The numerator of the fraction is the difference between the specific parameter describing a particular feature of the sanitation system and the current norm of the community regarding the parameter. This value is then divided by the current norm of the community regarding the parameter to indicate

how significant this difference is. Hence, the fraction makes the sub-index dimensionless, making it useful to compare two or more systems with each other in any community.

**Figure 1.** Structure of the sanitation sustainability index and its evaluation criteria.

Water efficiency (WE), energy efficiency (EE), and waste recycling efficiency (WRE) are dimensionless variables assigned to the technical sub-index. The WE variable is calculated by Equation (1), where VC is the typical amount of water consumption utilized for a single use of the sanitation system, including both water for flushing and other hygienic purposes like handwashing. VM is the mean of the volume of consumed water in the common sanitation system of the community. When VC ≥ VM, the value of WE should be considered zero.

$$\text{WE} = \frac{\text{V}\_{\text{M}} - \text{V}\_{\text{C}}}{\text{V}\_{\text{M}}} \,\text{\,}\tag{1}$$

The EE is calculated by Equation (2), where EC is the energy consumption for treating wastewater made from a single usage of the sanitation system, and EM is the mean energy consumption for wastewater treatment in common sanitation systems of the community. When EC ≥ EM, the value of EE should be considered zero.

$$\text{EE} = \frac{\text{E}\_{\text{M}} - \text{E}\_{\text{C}}}{\text{E}\_{\text{M}}},\tag{2}$$

WRE is the ratio of safely recycled waste to total waste production. This variable also evaluates the ability of a sanitation system to both treat and utilize produced waste.

For the economic sub-index, capital cost index (CCI), maintenance cost index (MCI), and direct economic benefits (DEBs) are suggested as the dimensionless variables. CCI and MCI are calculated by Equations (3) and (4), respectively. In these equations, the CCE is the estimated capital cost, and CCM is the mean capital cost for the common sanitation systems of the community. Similarly, the MCE is the estimated maintenance cost for a year, and MCM is the mean maintenance cost for the common sanitation systems of the community. If CCE ≥ CCM, then the value of CCI should be considered as zero. Similarly, if MCE ≥ MCM, then the value of MCI should be considered as zero.

$$\text{CCI} = \frac{\text{CC}\_{\text{M}} - \text{CC}\_{\text{E}}}{\text{CC}\_{\text{M}}},\tag{3}$$

$$\text{MCI} = \frac{\text{MC}\_{\text{M}} - \text{MC}\_{\text{E}}}{\text{MC}\_{\text{M}}},\tag{4}$$

DEB is a binary variable. When a sanitation system can produce economic benefits or has the potential that its economic benefit covers the capital and maintenance costs, then DEB should be 1, otherwise, it is 0.

The social sub-index includes acceptability and public health indicators as its relative variables. Both mentioned variables are qualitative, which must be turned into dimensionless quantitative variables through onsite investigations, and acceptability should reflect the cultural sanitation actions in the society. In this case, investigations should be performed by analyzing questionnaires that reflect the opinion of the users after experiencing the system. Therefore, the acceptability variable can be defined as the percentage of people who were satisfied after using the system and would use it again. For newly developed sanitation systems like ROS, user training can significantly increase the acceptability variable.

The public health indicator should reflect the hygiene aspects of the sanitation system. A wide range of considerations including safe treatment, recycling process, reduction of risks of incidence for sanitary diseases (e.g., diarrhea), total hygiene status of the system, especially where there is an interface with users or maintenance technicians, and efficiency in controlling public health concerns, e.g., reducing open defecation cases, are required to define this variable. Although several studies have been conducted on the social aspects of sanitation in different communities, there is no established standard survey to evaluate the acceptability and public health aspects of a sanitation system [4,27–29,32]. Therefore, regardless of the method of investigation, a value of 0 to 1, representing the evaluation criteria, should be assigned for the acceptability and public health variables.

Accordingly, for both acceptability and public health, the index is flexible for any appropriate and possible local application. The scoring can be done by the decision-maker or technician who is applying this index to the results of a local investigation as well as other appropriate data.

After evaluating all the described sub-indexes and variables, the SSI score is calculated as the arithmetic mean of all the values. For a specific community, when two or more sanitation systems are being compared, the system with the higher SSI is concluded to be more sustainable for implementation, and an SSI value closer to 1 reflects higher sustainability for implementation.

#### *2.2. Applicability of SSI for Sanitation System Implementation in South Korea*

To demonstrate SSI applicability, the SSI is calculated to evaluate the implementation of two onsite sanitation systems: a septic tank system and an ROS system. The systems are considered for implementation in a suburban residential area of Nowon District, Seoul, Republic of Korea to offer public hygiene services. For both sanitation systems, variables related to technical and economic sub-indexes were assigned based on the characteristics and assumptions of these systems, which were described in a previous study [12]. Table 1 presents the assumptions for calculating the SSI for both sanitation systems, including references that were used for assigning specific values to each parameter. A currency exchange rate of KRW 1100 for USD 1 is used, wherever applicable.

There is insufficient research on the social acceptability and public health issues for sanitation systems in Korea. However, considering the ancient sanitation practices in Korea as described by Han & Hashemi [5], along with other local pilot studies, it might be reasonable to consider a value of 0.7–0.8 for both social acceptability and public health indicators for the ROS system variables [20]. As using septic tank systems is quite common in both urban and rural areas of South Korea, a value of 0.9 was utilized for both the acceptability and public health variables.

A sensitivity analysis for the SSI scores calculated for both sanitation systems was conducted by applying a Δ = ±10% variation to each parameter. Additionally, to account for the lack of knowledge

and availability of data, statistical distributions for each variable were utilized to forecast the statistical distribution of the calculated SSI indexes through Monte Carlo simulation using Oracle Crystal Ball version <IP_ADDRESS> with 1,000,000 trials. Details of the assumptions and results of this statistical analysis are presented in the Supplementary Material.

**Table 1.** Assumptions for calculating sanitation sustainability index of septic tank and resource-oriented sanitation systems in South Korea.

† Including laboring costs for initialization and one-year maintenance services.

#### **3. Results**

#### *3.1. SSI Applicability for Evaluating the Proposed Implementation of Sanitation Systems in South Korea*

Figure 2 presents the results of the SSI sub-indexes evaluation for both mentioned sanitation systems in South Korea. The SSI was quantified as 0.42 and 0.71 for septic tank and ROS systems, respectively. Thus, notable differences between the calculated SSIs were observed, particularly for the ROS system, which shows better sustainability in the technical and economic sub-indexes. As described in previous studies, the ability of ROS systems to recycle waste and their economic benefits is significant [12,20]. According to the Republic of Korea, Ministry of Environment, there is an average recycling rate of 51.9% for wastewater generated from wastewater treatment facilities, such as septic tanks, in South Korea [35]. The wastewater produced in septic tank sanitation systems includes a mixture of urine, feces, hygienic materials (e.g., toilet paper), and flushing water. However, properly designed ROS systems can have a significantly higher WRE, approximately 0.7–0.9, by storing and treating urine and feces separately [5,20].

**Figure 2.** Comparison of sanitation sustainability index for septic tank and resource-oriented sanitation systems in South Korea.

The social sub-index of ROS systems is considered lower than that of a septic tank. Conducting in-depth studies on the social acceptability of sanitation systems in South Korea can provide a better assessment for this sub-index. Conducting safe, natural treatment methods for urine and feces, and providing sustainable operation monitoring, regular maintenance and training for users are beneficial actions for increasing the social sub-index scores of the ROS system.

#### *3.2. Sensitivity Analysis for SSI*

Figure 3 presents the sensitivity analysis for the studied sanitation systems. For the septic tank system, after social sub-indexes, the following descending order of variables in terms of their impact on SSI apply: EC, VC, MCE, CCE, and WRE. However, for the ROS system, DEBs and WRE have the greatest impact, while CCE, acceptability, public health, and MCE indicators have notable impacts. The sensitivity of other variables was negligible.

These results indicate that for South Korea, which has a notably long history in recycling human waste as fertilizer, the development of an ROS system for waste recycling and utilization can potentially increase the SSI. Additionally, reducing the CCE and MCE by utilizing local labor and materials can also significantly increase the ROS system sustainability.

#### *3.3. Statistical Distribution Forecast for SSI*

Figure 4 presents the results of forecasting the SSI statistical distributions for both sanitation systems. Results for 1,000,000 trials yielded a mean of 0.36 (95% CI = 0.24–0.50) and 0.67 (95% CI = 0.55–0.75) for septic tank and ROS systems, respectively. The calculated SSI scores for both systems (0.42 for septic tank system and 0.71 for ROS system) are within the 95% CI, and do not have a significant difference in the forecasted mean. Similar trends were observed for the forecasted statistical distributions of WE, EE, WRE, CCI, and MCI, and these results are presented as Supplementary Material.

**Figure 4.** Forecasted statistical distribution of sanitation sustainability index calculated for (**a**) septic tank and (**b**) resource-oriented sanitation systems in South Korea.

The results concluded that the SSI could be a reliable index as a means for evaluating the sustainability of a sanitation system, as well as comparing the sustainability of different sanitation systems.

#### **4. Discussion**

The proposed SSI can be considered a tool to evaluate the sustainability of any local sanitation system and its associated infrastructure. It can be used to evaluate the sustainability of a single sanitation system, as well as to compare two or more systems. The index includes sub-indexes, which can provide technical, economic, and social evaluations. Overall, SSI can be a useful tool for sanitation system designers, managers, and developers. Meanwhile, decision-makers can also use SSI to compare different systems to choose the most sustainable one for implementation.

The sub-indexes and their variables are based on the understanding of the sanitation status of the community, where the system is going to be implemented. Accordingly, the scope of the index is narrowed to one specific community. This means that the value of the index is specifically valid for a particular community and may differ between communities. This feature gives sufficient flexibility to the index, rendering it entirely replicable. Nevertheless, in case of availability of sufficient data reflecting the nation-wide sanitation status, SSI can also be used to evaluate sanitation systems at a national level.

The variables of all sub-indexes are also compatible with time. Community-based variables, such as VM, EM, CCM, and MCM, can be defined based on the predicted changes to the community (e.g., increase in population). Accordingly, the dimensionless index can also provide a vision about the sustainability of the assessed system in the future.

The flexibility and applicability of this index can be compared with that of the one suggested by Iribarnegaray et al., which also evaluates access to clean and safe water [36]. Most of the available indexes proposed to evaluate water and sanitation sustainability are useful in evaluating systems that are already implemented. Although all these indexes are defined with a similar objective, the SSI is used to evaluate the sustainability of sanitation systems before implementation, which can save time, money, and resources. Furthermore, its technical and economic sub-indexes are defined based on logical and simple equations, reflecting differences between the evaluated systems and the current norms of the community. Moreover, these sub-indexes can determine the potential of the system for waste recycling and reuse as well as provisions for economic benefits.

SSI applicability was demonstrated for evaluating the implementation of a septic tank and an ROS system in a suburban area of Seoul. Results indicated higher sustainability for the ROS system compared to the more commonly used septic tank system. Implementations of ROS systems are limited to the demonstration level through limited small projects.

A notable feature of the SSI is its use in determining the fate of wastes as well as the economic and social aspects of a sanitation system. Considering the high potential of an ROS system for waste recycling, it can be concluded that it is entirely sustainable in both technical and economic aspects. The index clearly shows that the implementation of the ROS has a higher capital cost, with the potential for providing direct economic benefits, which can cover both capital and maintenance costs.

With regard to social evaluation, the index assesses the acceptability and provision of public health services for a sanitation system. South Korea, along with some other Asian countries, has a historical background of using source-separated urine and feces as fertilizer [5]. Accordingly, ROS can be quite acceptable if more of them are implemented. Meanwhile, more efficient and hygienic maintenance and waste treatment processes can notably increase the social evaluation score of an ROS system. In addition, conducting a sensitivity analysis can determine the target parameters or sub-indexes of SSI for a specific sanitation system regarding a specific community. Accordingly, giving priority to these parameters might be useful to increase the sustainability of the sanitation system in the specific community.

The reliability of the SSI was examined through Monte Carlo simulation to forecast the statistical distribution of the calculated SSI scores. It became clear that the results were within the 95% CI. Accordingly, the index can be reliably applied to any other community with different settings when the only requirement for the SSI input is relevant local data.

#### **5. Limitations of SSI**

Although SSI is proposed to improve sanitation in communities worldwide, the approach described in this study may not be the ideal one.

For example, the economic sub-indexes are based on specific estimations that rely on the current financial status of the community. However, the economic situation of a community can be profoundly affected by unpredicted social events such as a pandemic.

Moreover, the social sub-indexes are heavily dependent on the availability of related studies and databases. Especially for newly developed sanitation systems, there is a demand for previous pilot projects that investigated the acceptability and efficiency of the system in improving public health by reducing the risk of sanitation-related illnesses. The investigation methods depend on the community culture and available resources for the investigation. The role of SSI is to reflect and simplify the results of these investigations. Accordingly, to use SSI, prior local studies on economic and social perspectives of the community are crucial.

#### **6. Conclusions**

In this paper, the SSI is proposed as an index to evaluate the sustainability of sanitation systems intended to be implemented in a community. The SSI is simple to calculate, and its variables are flexible, time compatible, and entirely dependent on the characteristics of the community where the system will be implemented. It considers the technical, economic, and social aspects of the system. Therefore, the SSI is a reliable indicator to evaluate different sanitation systems, compare their sustainability, and choose the most suitable type for a specific community.

The applicability of the SSI has been demonstrated for South Korea by evaluating the implementation of a septic tank and an ROS system. A sensitivity analysis was performed to determine the variables that had significant impact. Statistical distribution was forecasted for the SSI of both systems and proved that the calculated SSI is within the 95% confidence interval.

The SSI can evaluate the sustainability of any sanitation system, considering the current water and sanitation condition of the community before implementation. This feature of SSI can make it useful for choosing the best sanitation system for a community, especially in remote and rural areas where access to clean water and sanitation is limited and inadequate.

The index applies to any community, and its prerequisite is relevant technical, economic, and social data. Accordingly, the provision of comprehensive, relevant databases for the community is essential. The lack of such databases causes limitations, especially for calculating the SSI social sub-index. Consequently, the development of a standard survey to determine social acceptability, cultural sanitation aspects, and public health indicators will be advantageous to further develop the SSI. Thus, studies on customizing the SSI and defining new variables or sub-indexes for specific communities will make this index more beneficial.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2071-1050/12/17/6937/s1: Sustainability Evaluation Results for Implementation of Septic Tank and Resource-Oriented Sanitation Systems in South Korea.

**Funding:** This research received no external funding.

**Acknowledgments:** The author's profound gratitude goes to Eng. Farid Hashemi, for his kind support and efforts. This article was written during the peak of the COVID-19 pandemic. The author would like to express his deepest sympathies to people worldwide who have faced losses due to this pandemic. Sanitation and hygiene have become even more critical now, and the author will continue to contribute toward achieving global sustainable and adequate sanitation, especially for those in remote and rural areas. The author wishes for the day where no one is left behind regarding access to clean water and sanitation and hopes that everyone stays safe and sound.

**Conflicts of Interest:** The author declares no conflict of interest.

#### **References**

© 2020 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## *Article* **National Versus Local Sustainable Development Plans and Island Priorities in Sanitation: Examples from the Kingdom of Tonga**

#### **Ian White 1,\*, Tony Falkland <sup>2</sup> and Taaniela Kula <sup>3</sup>**

Received: 22 October 2020; Accepted: 9 November 2020; Published: 11 November 2020

**Abstract:** Sanitation, water supply, and their governance remain major challenges in many Pacific Island countries. National sustainable development strategies (NSDSs) are promoted throughout the Pacific as overarching improved governance instruments to identify priorities, plan solutions, and fulfill commitments to sustainable development. Their relevance to local village-level development priorities is uncertain. In this work we compare national priorities for sanitation in NSDSs with those in village community development plans (CDPs) and with metrics in censuses from the Kingdom of Tonga. Tonga's Strategic Development Frameworks (TSDFI 2011–2014 and TSDFII 2015–2025) were developed to focus government and its agencies on national outcomes. From 2007 to 2016, 136 villages throughout Tonga's five Island Divisions (IDs) formulated CDPs involving separately 80% of women, youth, and men in each village. It is shown that censuses in 2006 and 2016 reveal linked improvements in water supply and sanitation systems but identify IDs with continuing challenges. It is found that sanitation and water are a national priority in TSDFI but are absent from the current TSDFII. In contrast, analysis of CDPs, published just after TSDFII, show in one ID, 53% of villages ranked sanitation as a priority and marked differences were found between IDs and between women, youth, and men. CDPs' sanitation priorities in IDs are shown to mostly correspond to sanitation and water metrics in the censuses, but some reflect impacts of natural disasters. Explanations for differences in sanitation priorities between the national and local development plans, as well as suggestions for improving NSDS processes in island countries, are advanced.

**Keywords:** sustainable development strategies; community development plans; small island developing states; governance; sanitation; water supply; hygiene; WASH; census results; top-down versus bottom-up; gender and age; SDG6

#### **1. Introduction**

The combined challenges of climate change and economic development have long been recognized as major threats to the sustainability of small island developing states (SIDS), impacting especially vital water and sanitation services [1–3]. Water supply and sanitation systems remain continuing challenges in the Pacific region which was the only region in the world where there was an increase in open defecation between 2000 and 2015 [4].

National sustainable development strategies (NSDSs) [5] have been seen as an efficient way for SIDS to identify national challenges, plan their solutions, assign resources and responsibilities, and fulfill country commitments to international and regional agreements and programs, particularly the United Nations (UN) Sustainable Development Goals (SDGs) and UN SIDS action programs [3]. Part of their efficiency stems from the fact that they are mainly top-down processes, often encouraged, assisted, and supported by external agencies. The relevance of such governance processes imported into dispersed small island communities in Pacific Island countries (PICs) has been questioned [6]. PICs characteristically have well-developed local institutions, resilient social systems, a sensitivity to environmental change, and a high degree of equity [7]. These strengths make PICs well suited to bottom-up planning processes, but these are generally time consuming [8]. In this work, using a valuable example from a multi-island PIC, the Kingdom of Tonga, comparison is made between the planning priorities given to sanitation in top-down national processes and bottom-up village development planning processes.

Improvements in water, sanitation, and hygiene (WASH) have long been recognized as one of the keys for the continued development of PICs [1–3]. The incidence of diarrheal diseases in PICs is, on average, four to five times higher than in larger countries in the Oceania region [9] and is mainly linked to contaminated drinking water as a result of poor sanitation and hygiene [10]. This linkage was one of the reasons that Oceania as a region did not meet the UN's 2015 Millennium Development targets for water and sanitation [11].

Sanitation in SIDS remains a significant challenge for many interacting reasons. Dispersed island communities, restricted land areas, limited and sometimes brackish water supply, El Niño Southern Oscillation (ENSO)- and Pacific Decadal Oscillation (PDO)-related droughts [12], frequent extreme events, including intense tropical cyclones (TCs) [13], easily polluted surface and limited groundwater, coupled with a wide range of population densities, variable island geologies and geomorphologies, and restricted land and financial resources mean that identifying locally acceptable, safe, appropriate, and affordable sanitation systems with minimum impacts on fragile island environments is problematic. The most difficult are islands which rely on variable rainwater as their only source of water for all purposes [10].

Improved governance and accessible information are seen as central to improved WASH outcomes [14], particularly in SIDS. NSDSs have been promulgated as overarching, efficient, integrated governance instruments to identify and solve national development challenges and address UN SDGs [15]. The South Pacific Kingdom of Tonga presents an opportunity to contrast identified sanitation priorities in top-down national and bottom-up village planning processes. Tonga's national development planning instrument, the Tonga Strategic Development Framework 2015–2025 (TSDFII) [16] was launched in 2015 after three months of senior-level consultations and a three-month review by ministries. TSDFII built on experiences from the Tonga Strategic Development Framework 2011–2014 (TSDFI) [17]. TSDFII and TSDFI, present an integrated vision of the direction the government and its agencies' plan to pursue as well as contribute to Tonga's international and regional commitments.

A much lengthier village level development planning process occurred throughout all Island Divisions (IDs) in Tonga between 2007 and 2016. This created Community Development Plans (CDPs) in rural villages throughout Tonga's five IDs under the Ministry of Internal Affairs (MIA) and was facilitated by a non-government organization, Mainstreaming of Rural Development Innovation Tonga Trust (MORDI TT), with support from donors [18]. CDPs ranked local village priority development issues which were prepared and endorsed by a minimum of 80% of each village community. In the past, only men had been involved in local planning. Breaking from tradition, the CDP process also included women and youth who ranked priorities separately from men. In 2016, 136 CDPs out of Tonga's 151 rural villages, were presented to the then Prime Minister [18]. Currently, 117 of the CDPs are available for analysis [19].

It was shown recently [20] that the high priority given to improving water supply in village CDPs universally throughout all Tonga's five IDs contrasts with the omission of water supply from planned outcomes in TSDFII, despite TSDFII's claim that it addresses UN SDG6 on water and sanitation. Here, the priorities given to sanitation in both TSDFII and in the preceding TSDFI are compared with its ranked priority in the available CDPs. These are also compared with census data from 2006 and 2016 on sanitation type and available water sources at the ID level.

Several indices and indicators have been proposed to monitor performance in WASH [21,22]. The sanitation sustainability index (SSI) has been introduced recently as an indicator for evaluating the sustainability of sanitation systems [23]. The strength of SSI is that it includes integrated measures of the technical, social, environmental, and economic aspects of local community sanitation systems. Unfortunately, in PIC rural villages, even technical information is often absent. What are available usually are national census data on water sources and sanitation types together with often limited hydrological data.

Four questions are addressed in this work:

These questions are addressed at the ID level.

Census data on demographics and household water supply sources and sanitation systems from the last two censuses in 2006 and 2016 [24,25] in Tonga are compared at the ID level as well as for the capital area, Greater Nuku'alofa. The relation between sanitation type and water source used are explored. The emphasis given to sanitation in both TSDFI and TSDFII [16,17] is then examined and compared with that given to other infrastructure services. An analysis is presented of the ranked priorities given by women, youth, and men, as well as aggregate village priorities for sanitation in the available CDPs [19] from villages in all IDs. Relationships between CDP priority rankings for sanitation and census sanitation type and water source data are explored. Underlying reasons for differences in top-down versus bottom-up development priorities for sanitation are discussed and options for improving NSDS processes in PICs are given.

#### **2. Materials and Methods**

#### *2.1. Study Location*

The Kingdom of Tonga's population of close to 101,000 people live in 169 islands clustered in five IDs with approximate land area of 750 km2. These are dispersed over 700,000 km2 of the southwestern Pacific Ocean (Figure 1). Its islands border the seismically active Tonga trench. Tonga's western islands are volcanic in origin, but its eastern islands are geologically different, being uplifted coral limestone and sand islands. Most of the eastern islands, including Tongatapu, the largest island and location of the capital Nuku'alofa, have a covering of rich volcanic soil deposited from eruptions in the western islands. Volcanic eruptions, earthquakes, tsunamis, TCs, storm surges, and droughts and floods linked to ENSO and the PDO are frequent natural hazards. Recent TCs that have devastated parts of Tonga include TC Ian (2014), TC Gita (2017), and TC Harold (2020).

There is a gradient in annual rainfall across Tonga varying from 1750 mm in the south to 2300 mm in the north, influenced by proximity to the South Pacific Convergence Zone (SPCZ). Annual rainfall variability is moderate with a mean coefficient of variability of 0.21 for the period 1947 to 2019 and decreases from north to south. There are no long-term trends in available annual rainfall [20], which is consistent with climate change projections for Tonga [12]. The Kingdom has a wetter season from November to April followed by a drier season from May to October, also influenced by the position of the SPCZ [26].

**Figure 1.** Map of the South Pacific Kingdom of Tonga, main Island Divisions and population centers [27].

Water supply in Tonga is mainly sourced from household rainwater harvesting systems and groundwater. Water is supplied from groundwater lenses or springs in the carbonate and sand islands. Many of the volcanic islands do not appear to have useable groundwater [27]. Because seawater underlies groundwater lenses, groundwater salinity in Tonga varies from fresh to brackish and even saline, depending on island geology, size, pumping method and rate, and ENSO and PDO conditions. Springs and groundwater used in 'Eua and most of the groundwater in Tongatapu have lower salinities than groundwater in Vava'u and Ha'apai [27]. Tongans prefer rainwater for drinking, and groundwater is used for all other purposes including toilet flushing. The main sanitation systems are cistern flush toilets or pour flush toilets discharging into septic tanks and pit toilets. Both septic tanks and pit toilets have the potential to contaminate groundwater.

In 2016, about three quarters of Tongans lived on the main island Tongatapu with Greater Nuku'alofa, the capital, having over a third of the country's population. About a quarter of the population is spread over the Kingdom's other four IDs (Figure 1). About 55% of the population is under the age of 25 with youth, aged 14 to 24, making up nearly 19% of the total population [25]. Gross domestic product (GDP) in 2017 was estimated to be US\$5900 per person with an annual growth rate around 2.5% [28]. GDP varies widely between IDs with Tongatapu being 15% above the national average in 2013, while Ha'apai was 40% below the national average. Natural disasters have been estimated to cost 4.4% of GDP and TC Ian in 2014, which affected 70% of the population of Ha'apai, severely damaged 75% of the housing stock and cost 11% of GDP [16].

Piped water is supplied from groundwater or spring sources [27]. In Nuku'alofa, 'Eua, and population centers on Vava'u and Ha'apai, piped water is supplied by the Tonga Water Board. Village Water Committees are responsible for piped water supply in villages throughout Tonga. Village piped water supply is mostly intermittent unlike in Greater Nuku'alofa where supply is continuous.

In PICs, traditionally, sanitation was either a personal or household responsibility. In Tonga, sanitation is overseen by the Ministry of Health and, in villages, responsibility is delegated to Village Water Committees (VWCs). There are no public reticulated sewerage systems in Tonga and sanitation is mainly a household responsibility.

#### *2.2. Demographics, Water Sources, and Sanitation Systems*

The censuses in 2006 and 2016 [16,17] provide details of the national, ID, district, and village level population distribution as well as urban/rural data and can be used to identify changes. This work concentrates on the ID level. Census results are also used here to compare the use of different water sources for all non-drinking purposes, which includes use for sanitation, and to compare sanitation systems used by households across IDs and in Greater Nuku'alofa.

The very limited data on water use from different sources indicates that piped water systems in Tonga supply households (HH) with almost an order of magnitude more water than rain tanks [27]. Here, we make use of the water source ratio (WSR) as a measure of the ID availability of water for all non-drinking purposes [20]:

$$\text{WSR} = \text{(HH supplied by rain bands)} \text{(HH with pipe water supply)} \tag{1}$$

Sanitation systems in Tonga fall into two groups—those that require little or no water such as pit toilets and pour flush toilets, and cistern flush toilets that require more water. We introduce the sanitation type ratio (STR) as a crude, relative measure of improved sanitation systems:

$$\text{STR} = \text{(HH with pt} + \text{HH with pour flussh toilets)} \text{(HH with cistern flush toilets)} \tag{2}$$

The use of these ratios is a result of the limited data available on water and sanitation systems and their use. We use WSR and STR to compare IDs and the capital Nuku'alofa. If availability of water is a significant factor in the choice of sanitation system [23], then the hypothesis is that the two ratios should be related.

#### *2.3. Tonga Strategic Development Framework 2011–2014, TSDFI*

TSDF1 [17] was developed after the first full parliamentary elections in Tonga. It built on the consultative process in the previous National Strategic Development Framework in October 2009. Its aim was to provide principles and directions to guide the work of the government administration over its four-year term, 2011 to 2014. It involved consultations over a nine-month period carried out in all five IDs in Tonga [29].

The government's vision for TSDFI was, "To develop and promote a just, equitable, and progressive society in which the people of Tonga enjoy good health, peace, harmony, and prosperity, in meeting their aspirations in life." The government's objectives are expressed at two levels: At the top level are the nine primary Outcome Objectives that contribute to the vision, and at the second level are four enabling themes that support the achievement of these outcomes. The enabling themes are more efficient and effective government, improving macro-economic and fiscal management, sustainable and accountable public enterprises, and coordinated and integrated approach to development partners. The Outcome Objectives have 27 Associated Strategies (ASs) and the enabling themes have a further 15 ASs. The ministries responsible for each Outcome Objective were identified and each were linked to Millennium Development Goals [17].

The Ministry of Finance and National Planning (MFNP) led preparation of TSDFI which was supported by the Australian Agency for International Development (AusAID) and the planning process was facilitated by the Asian Development Bank (ADB).

TDSFI was scanned for references to water, freshwater, rainwater, groundwater, water supply, WASH, sanitation and hygiene, and the Outcome Objectives and ASs were examined for their relevance to sanitation. The relative weight of sanitation to infrastructure and other services was determined.

#### *2.4. Tonga Strategic Development Framework 2025–2015, TSDFII*

The TSDFII [16] is structured differently to and is more complex than the preceding TSDFI. TSDFII is " ... the overarching framework of the planning system in Tonga. It provides an integrated vision of the direction that Tonga seeks to pursue." [16]. TSDFII is the top of a cascading system of planning and budgeting which is intended to guide:

TSDFII identifies government priorities, assigns ministerial responsibilities, and aims to focus resources. TSDFII is arranged in a hierarchy where 29 Organizational Outcomes (OOs), grouped under three institutional pillars and two input pillars, feed into seven desired National Outcomes (NOs) that in turn feed into the single Outcome: "More inclusive sustainable growth and development" which supports the single planned National Impact of TSDFII: "A more progressive Tonga supporting a higher quality of life for all" which supports the motto of TSDFII, given by the reformer monarch Tupou I: "God and Tonga are my inheritance". TSDFII also lists 153 Strategic Concepts (SCs) which were issues raised during the consultation process but lie outside TSDFII but are intended as aids to sector, district and ministry, department, and agency planning and budgeting [16].

MFNP led development of TSDFII, supported by the ADB. It used wide but fairly rapid three month high-level consultations with "key sectors of the economy including the community (district and town officers), church leader forums, non-government organizations, and private business forums, including all the main sectors: agriculture, fisheries, tourism, commerce, manufacturing, and construction" [16]. Consultation meetings were held throughout Tongatapu and the IDs of 'Eua, Ha'apai, and Vava'u in the period between October 2014 and December 2014. The northern Ongo Niua ID was not covered. These consultations, together with lessons learnt from TSDFI, were incorporated into drafts of TSDFII which were circulated to government ministries, departments, and agencies for further review in early 2015 [16].

The TSDFII was scanned for references to water, freshwater, rainwater, groundwater, water supply, sanitation, hygiene, and WASH and the planned NOs, OOs, and SCs were examined for their relevance and applicability to sanitation. The weight given to these relative to other infrastructure and other services was determined.

#### *2.5. Community Development Plans, 2016*

Development of village CDPs [18] began in 2007, under the Local Government Division of the MIA. The CDPs were a response to the then National Vision in TSDFI "A Progressive Tonga Supporting Higher Life for All". Consultations throughout rural villages in Tonga's five IDs were implemented by the NGO Mainstreaming of Rural Development Innovation Trust Tonga (MORDI TT). The CDP process was supported by the International Fund for Agricultural Development (IFAD), UNDP, AusAID, and the Tonga Government. One of the requirements of the project was participation of 80% of the population of each rural village in the development, ranking of priorities, and endorsement of the village CDP. Priorities were ranked separately by women, youth (aged 14 to 24 years), and men. Consultations involved a lengthy process which culminated in District Officers and Town Officers

of 136 village communities presenting their CDPs to the then Prime Minister on 4 October 2016 [18]. The CDPs are really ranked lists of local village concerns.

During the planning process the Department for Local Government was transferred from the Prime Minister's Office to the Ministry of Training, Employment, Youth, and Sports, and then to the MIA [18]. Analysis of and response to CDPs appear to have been deferred by these moves. We have not found any analysis of the valuable information on village development priorities in CDPs apart from our analysis of water supply [20].

Of the 136 CDPs presented, 117 are available on-line [19]. These represent 77.5% of all rural villages in Tonga. CDPs were downloaded and the priority rankings of each village that mentioned sanitation were recorded (Table S1). Particular note was made when sanitation ranked in the top three priorities for women, men, and youth, which also provided a village average. Village level results were aggregated to percentage of villages in each ID. Also recorded was the percentage of villages within each ID that ranked sanitation anywhere in their list of priorities.

#### **3. Results**

#### *3.1. Changes in Demographics*

Table 1 shows the demographic data from the 2006 [24] and 2011 [25] censuses for Tonga, for the five IDs, and for Greater Nuku'alofa (GN).

**Table 1.** Demographic data for Tonga, Island Divisions, and Greater Nuku'alofa from the 2006 [24] and 2016 [25] censuses and the percent change that has occurred since 2006.

<sup>1</sup> Ongo Niua includes Niuafo'ou and Niuatoputapu. <sup>2</sup> Greater Nuku'alofa is made up of the districts of Kolofo'ou and Kolomotu'a in Tongatapu. <sup>3</sup> It appears that the area given for Tongatapu of 260 km2 is the area occupied by villages.

Table 1 shows that in 2016 almost 75% of Tongans live on the main island Tongatapu, with Greater Nuku'alofa having 35% of the total population. About 25% of the population are spread over the Kingdom's other four IDs. The 2016 census defined 77% of the population as rural, although this includes villages within Greater Nuku'alofa [25].

Net migration from Tonga between 2006 and 2016 is evident in Table 1 but with significant inwards migration from the outer IDs to the main island Tongatapu and to Greater Nuku'alofa (Figure 2). The overall population density has decreased correspondingly in Tonga, with significant decreases in population density in Ha'apai and Ongo Niua partially offset by increases in Tongatapu. The population decrease in Ha'apai may be partly due to impacts of TC Ian in 2014 [16].

**Figure 2.** Percentage change between 2006 and 2016 in the population of Tonga's five Island Divisions and Greater Nuku'alofa (GN'a) relative to 2006.

Table 1 also reveals an overall increase in the number of households driven by large increases in Tongatapu and Greater Nuku'alofa but offset by decreases in the outer IDs, especially Ha'apai and Ongo Niua. Partly as a result of the shift in population (Figure 2) and the change in the number of households, the number of people per household decreased in Tonga by 5.5% between 2006 and 2016 with similar decreases across all IDs and Greater Nuku'alofa. Paradoxically, there has been an apparent increase in the number of villages in Tonga counted in the censuses, driven mainly by a large apparent increase in Vava'u.

#### *3.2. Changes in Water Sources*

Because of the intimate connection between water and sanitation, the use of different water sources is first examined. There is limited data on the amount of water used for different purposes in Tonga [20,27,30–32]. It is clear, however, that the greatest volume of household water use is for non-drinking purposes such as toilet flushing, washing, and bathing [33]. Table 2 lists the percentage of households accessing water from different sources for non-drinking purposes and the percentage changes in each between the 2006 and 2016 censuses for Tonga as a whole, the five IDs, and Greater Nuku'alofa.

For Tonga as a whole, Table 2 reveals a 6% increase in access to piped water supply, a 26% decrease in the use of household rank tanks, a large 62% decrease in the use of household water wells, and 40% decrease in other sources (not specified in the censuses) for non-drinking purposes between 2006 and 2016. For the IDs, 'Eua, and Ongo Niua had significant increases in access to piped water but, in Vava'u and Ha'apai, there was very little change in piped water supply. The national decrease in using household rainwater tanks was driven by very large decreases in 'Eua and Tongatapu and a smaller decrease in Ongo Niua. These decreases could be the result of improvements in piped water supply between 2006 and 2016 in 'Eua, Tongatapu, and especially Nuku'alofa, but also in Ongo Niua [27,34]

Although there was limited overall use of household wells in 2006, there were dramatic decreases in their use in 2016 in all IDs. In 'Eua and Vava'u household wells were abandoned as a source of water for non-drinking purposes in the 2016 data and use substantially reduced in Tongatapu, Ha'apai, and Greater Nuku'alofa. Household groundwater wells are easily contaminated by household sanitation systems such as pit toilets and leaking septic tanks [27].

**Table 2.** The percentage of households in Tonga, each Island Division, and Greater Nuku'alofa accessing water for non-drinking purposes from different water sources from the 2006 [24] and 2016 [25] censuses and the percentage change in sources relative to 2006.

Because non-drinking water use is the largest volumetric demand for water [33], the WSR, defined in Equation (1), provides a measure of the difficulty of meeting non-drinking water demand in villages and islands. This is because roof areas used to harvest rainwater are usually small and are often not very efficient, and average household size (Table 1) is relatively large [15]. The available data indicates that in outer islands, rain tanks supply about 20 L/person/day [30–32]. Figure 3 compares the WSP for Tonga's IDs as well as Greater Nuku'alofa for the 2006 and 2016 censuses.

**Figure 3.** Water source ratio, defined in Equation (1), for non-drinking water uses in Tonga's Island Divisions and Greater Nuku'alofa (GN'a) using data from Table 2 for 2006 and 2016 censuses.

Ha'apai and Ongo Niua IDs stand out in Figure 3, with a much larger proportion of their non-drinking water use being supplied from household rain tanks. The increased access to piped water between 2006 and 2016 in 'Eua, Tongatapu, Ongo Niua, and Greater Nuku'alofa is also evident in Figure 3. In Vava'u and Ha'apai, WSR actually increased between 2006 and 2016 indicating a greater dependency on rain tanks. In these Island Divisions and in Ongo Niua, toilet flushing, washing, and bathing are more dependent on rainwater harvesting than elsewhere in Tonga.

#### *3.3. Changes in Sanitation Systems*

Table 3 lists the percentage of households using different types of sanitation systems in Tonga, in IDs, and in Greater Nuku'alofa from the 2006 and 2016 censuses.

**Table 3.** The percentage of households in Tonga, Island Divisions, and Greater Nuku'alofa using different types of toilets and the percentage changes between 2006 [24] and 2016 [25] relative to 2006.

Between 2006 and 2016, dramatic changes are evident in Table 3 in the household use of different toilet systems in Tonga. Nationally, there was a 17% increase in the use of cistern flush toilets with a corresponding significant decrease in the use of manual pour flush toilets and a dramatic drop in the percentage of houses using pit toilets. Although the other toilet category is nationally very small, 1% or less, there was a major increase in use of this unspecified category.

All IDs increased access to household cistern flush toilets over the period 2006 to 2016 with the largest percentage increase in Ongo Niua and the smallest increase in Greater Nuku'alofa due to the already large percentage of households there with cistern flush toilets in 2006. All IDs also showed a large reduction in the use of pit toilets, with the largest reduction being in the main island of Tongatapu and the smallest, although still an appreciable reduction of 30%, in Ha'apai. 'Eua, Tongatapu, and Greater Nuku'alofa showed significant decreases in the use of manual pour flush toilets which, nationally, were offset by increases in their use in Vava'u and Ha'apai and a major increase of almost 230% in Ongo Niua. The "other" toilet category is not specified in either census, so it is uncertain why use of this category increased across all IDs. The 2006 census provided statistics on households which had no access to toilet facilities. This category is missing from the 2016 census and it may be that the increase in the other toilet facilities between 2006 and 2016 in Table 3 is due to the absence of the no toilet category in the 2016 census [24,25].

A measure of improvements in sanitation technology is the STR, defined in Equation (2). Figure 4 plots the STR for Tonga's IDs as well as Greater Nuku'alofa for both censuses.

**Figure 4.** Sanitation type ratio, defined in Equation (2), for Tonga's Island Divisions and Greater Nuku'alofa (GN'a) using data from Table 3 for 2006 and 2016.

Figure 4 demonstrates that STR halved between 2006 and 2016 for Tonga and for all IDs and also for Greater Nuku'alofa. In 2006, Ongo Niua had the highest STR with Tongatapu the lowest. STR in Greater Nuku'alofa is half that of Tongatapu in both census years. In 2016, STR is highest in Ha'apai but STR remained lowest in Tongatapu. The results reflect the increases in household use of cistern flush toilets across all IDs in Table 3.

Of the many factors that determine choice of sanitation systems [23], one hypothesis is that the availability of adequate household water supply is a strong determinant. Figure 5 shows the relation between WSR and STR for Tonga's IDs and Greater Nuku'alofa using the 2006 and 2016 census results.

**Figure 5.** Relationship between the sanitation type ratio (STR), defined in Equation (2), and the water source ratio (WSR), defined in Equation (1), for non-drinking water uses for Tonga's Island Divisions and Greater Nuku'alofa (GN'a) from the 2006 and 2016 censuses.

For the 2006 data the relation between STR and WSR is given by:

$$\text{STR} = (2.2 \pm 0.1). \text{ WSR} \tag{3}$$

The relation in Equation (3) has coefficient of determination R2 = 0.93 and is highly significant (*p* < 5.10<sup>−</sup>6). The relation for the 2016 data is:

$$\text{STR} = (1.0 \pm 0.1). \text{ WSR} \tag{4}$$

The relation in Equation (4) has R2 = 0.78 and is very significant (*p* < 5.10<sup>−</sup>4). Equations (3) and (4) reveal that the census data demonstrate a strong correlation between the sanitation type used by households in Tonga and the source of water available to meet non-drinking water demands. They also show the marked improvement in STR relative to WSR between 2006 and 2016.

#### *3.4. Sanitation Priorities in TSDFI*

To support the Government's vision for Tonga, given in Section 2.3, the TSDFI identified nine Outcome Objectives which are listed in Table 4 together with the number of Associated Strategies (ASs) for each Outcome Objective.

**Table 4.** The Outcome Objectives and Associated Strategies of TSDFI. Shown in parentheses are the number of sub-Associated Strategies [17].

Almost 30% of the ASs in Table 4 are linked to the Infrastructure Outcome Objective 3.

The word "sanitation" occurs 10 times throughout TSDFI. In 9 out of the 10 occurrences it occurs in the phrase "water and sanitation", emphasizing the intimate link between them. Table 5 compares the emphasis given to various services linked to infrastructure with that given to water and sanitation. Because of cross references in the ASs, several of the services are mentioned in more than one AS so the total of mentions is more than the number of ASs.

In Table 5, nearly 17% of the total references to services in ASs in TSDFI concern water and sanitation. This includes a mention of solid and liquid wastes under the wastes AS, part of which involves the disposal of septage from septic tanks. The emphasis on water and sanitation is equal to that for energy and for information and communications and half that given to transport.

**Table 5.** The number of references to different services in Associated Strategies under the Infrastructure Outcome 3 in TSDFI.

One of the 27 ASs (nearly 4%) solely concentrates on water and sanitation under Infrastructure Outcome Objective 3. TSDFI lists AS 13: "Maintaining and expanding access to safe water and sanitation for all communities." TSDFI provided performance indicators for this Strategy:

TSDFI clearly identified water and sanitation as linked national priorities to be included by relevant ministries and agencies in their corporate plans and annual reports. In many PICs, sanitation falls under the Ministry of Health. TSDFI did not, however, include sanitation or hygiene under the Improved Health Outcome Objective 6 (Table 4). Hygiene is only mentioned once in TSDFI in a discussion of the necessity for water and sanitation legislation to ensure "improvement of the hygiene of sanitation facilities". There is no reference to WASH in TSDFI.

#### *3.5. Sanitation Priorities in TSDFII*

The seven desired NOs in TSDFII [16] are:

The five pillars consist of three institutional pillars and the two input pillars:

#### **Institutional Pillars:**

#### **Input Pillars:**

These five pillars have 29 linked OOs.

Table 6 shows the number of OOs and SCs focused on services. All are listed under the Infrastructure NO E, except wastes, which was listed under the Environment NO F.

**Table 6.** The number of Organizational Outcomes and Strategic Concepts assigned to infrastructure services in TSDFII [16]. The total number of each are in parentheses.

Over 17% of the total OOs in TSDFII are the services listed in Table 6. Energy, transport, information and communications, building and structures, and wastes made up almost 3.5% each of the total OOs listed. Not one OO mentions water and/or sanitation in contrast to TSDFI which identified water and sanitation as a linked national priority under Infrastructure Outcome Objective 3.

Accompanying the OO are 153 SCs. Almost 21% of SCs involved the services in Table 6 but only one references water supply. Transport and information and communications each scored 6% of the SCs in contrast to water, 0.7%, and there is no mention of sanitation in any SC.

Under the natural resources pillar, within OO 5.2, "Improved use of natural resources for long term flow of benefits, SC b) records: "improve the management and delivery of safe water supply for business and households." There are no water supply key performance indicators (KPIs) associated with OO 5.2 SC b), so there is no way to measure performance. Since SCs are only considered an aid to planning there is no pressure for any ministry to address this SC.

Under the Health component of the Social Institutions Pillar, "Percentage of population with safe water supply" is listed as a KPI but has no associated SC or OO. Without this KPI being tied to an OO or an SC there is no guarantee that it would be addressed in ministry corporate plans or reports.

Sanitation is not mentioned in any of the 29 OOs or 153 SCs and it does not appear in any of the KPIs. The word "sanitation" only appears twice in TSDFII. In Annex 1 of TSDFII, "water and sanitation management" is mentioned as one of a long list of action topics of the Small Developing Island Countries Action Agenda in the SAMOA Pathway [3]. In Annex 2, TSDFII lists how NOs contribute to the United Nations SDGs. TSDFII claims that NOs F, E, and B, listed above, all contribute to fulfilling Tonga's commitments to SDG6: "Ensure availability and sustainable management of water and sanitation for all." There are no OOs or SCs under NO F, E, or B involving sanitation and water supply is only included as a single SC under NO F. TSDFII does not include any mention of hygiene or WASH.

The absence of water and sanitation from TSDFII after their inclusion in TSDFI is surprising and leaves the impression that water and sanitation are no longer sustainable development issues in Tonga despite the disparities between IDs revealed in the censuses.

#### *3.6. Village Community Development Plans (CDPs)*

Village CDPs are designated as plans. In practice, however, the available documents consist of ranked priorities of challenges to village development from women's, youths', and men's perspectives. There are no identified strategies for addressing challenges and no assignment of responsibilities or estimates of resources needed to address priorities. Table 7 provides details of the village CDPs that were available for analysis in each ID [19].

In total, 117 CDPs of the original 136 that were presented in 2016 were available on-line [19]. These available CDPs are 77.5% of the 151 rural villages in Tonga (Table 7). CDPs for the main island Tongatapu, excluded the districts of Kolofo'ou and Kolomotu'a that make up Greater Nuku'alofa, so CDPs for Tongatapu in Table 7 represent rural areas of the main island. Table 7 reveals that only five of the 27 villages in Ha'apai had accessible CDPs. This may be due to TC Ian which severely damaged 75% of the housing stock on Ha'apai in 2014 [16].

Table 7 shows for Tonga as a whole, the median number of priority issues identified by women and men were the same while youth identified slightly less. Ongo Niua Island Division villages identified the least number of priority issues while Ha'apai Island Division villages identified the most. Youth in 'Eua identified slightly more priority issues than elsewhere. The maximum number of priorities identified for women, youth, and men in any village was 12, 11, and 12, respectively, while the minimum number was 4, 3, and 3.

#### *3.7. Sanitation Priorities in Village CDPs*

None of the women, youth, or men in any of the villages throughout Tonga's IDs identified sanitation as their highest priority concern. Only 4% of villages identified sanitation as their second priority with women (8%) nationally having a higher concern than men (3%). None of the youth in any ID rated sanitation as their second priority (0%). The highest average second priority concerns over sanitation were in Ha'apai (7%) and the lowest were in Tongatapu (1%). In Ha'apai women in 20% of villages rated sanitation as their second priority but none of the youth and men in Ha'apai rated sanitation as their second priority (0%).

Table 8 lists the percentage of villages that ranked sanitation within their top three priorities.

**Table 8.** The percentage of villages throughout Tonga's Island Divisions, as well as Tonga collectively, which listed sanitation within their top three priorities in terms of women's, youths', and men's perspectives and the average of all three.

Overall, 9% of villages across Tonga in Table 5 placed sanitation within their top three priorities with women again showing more concern about sanitation than men. In contrast, youth in Tonga had little priority concerns about sanitation. The most concern about sanitation within the top three ranked issues was in the Ha'apai ID with both women and men showing equal concern (40%), in contrast to the absence of concern of youth. Tongatapu showed the least concern over sanitation (1%). Only women in 2% of the villages in Tongatapu ranked sanitation within the top three priorities.

Figure 6 plots the percentage of villages in IDs which identified sanitation as a concern in their list of all identified village priorities.

**Figure 6.** Percentage of villages in Island Divisions and in Tonga who ranked sanitation as a priority issue within their list of challenges to village development. Women's, youths', and men's priorities are given together with the average.

For Tonga as a whole, 20% of villages identified sanitation as a priority for village development. Women in Tonga expressed more concern about sanitation (32%) than men (20%) who were more concerned than youth (8%). The ID with the highest overall concerns about sanitation was Ha'apai (53%) with women and men having equal concerns (60%) and youth less (40%). The ID with the lowest number of villages identifying sanitation as a priority was Tongatapu (5%). There, women also expressed more concern (10%) than men or youth (both 2%). Women consistently identified sanitation as a concern in their village, more than men and youth, except in Ha'apai where women and men's concerns were equal.

The CDPs analyzed here were developed between 2007 and 2016, a period covered by both the 2006 and 2016 censuses. To determine if the distribution of the percentage of villages in IDs with percentage of priority sanitation concerns (PSC) is related to the Island distributions of STR (Figure 4), Figure 7 shows the relationship between PSC and STR.

The data in Figure 7 showed no significant relationships between PSC and STR for either census. The results, however, and the impact of a major tsunami on the ID suggest that the data for Ongo Niua may be outliers. If those results are omitted, a strong relationship is found for the other four IDs for the 2006 STR data:

$$\text{PSC}(\%) = (\text{36 } \pm 4). \text{ STR} \tag{5}$$

Equation (5) has R<sup>2</sup> = 0.96 and is very significant (*p* < 0.005). The relationship for the 2016 STR data is:

$$\text{PSC } (\%) = (68 \pm 10). \text{ STR} \tag{6}$$

Equation (6) has R2 = 0.93 and is significant (*p* < 0.01). The difference in the coefficient between Equations (5) and (6) is due to the decrease in STR between 2006 and 2016 caused mainly by the large decrease in pit toilets.

Because of the strong relationship between STR and WSR, defined in Equations (3) and (4), there are also significant relationships between PSC and WSR for the 2006 Census results:

$$\text{PSC } (\%) = (80 \pm 16). \text{ WSR} \tag{7}$$

Equation (5) has R<sup>2</sup> = 0.89 and is significant (*p* < 0.02). The relationship for the 2016 WSR data is:

$$\text{PSC } \text{(\%)}= \text{(}69 \pm 24\text{)}. \text{ WSR} \tag{8}$$

Equation (6) has R2 = 0.74 and is weakly significant (*p* < 0.07). It is noted that within the standard errors of the coefficients in Equations (7) and (8), the two coefficients are not statistically different (*p* > 0.1). Combining the 2006 and 2016 data for all IDs except Ongo Niua results in the relationship:

$$\text{PSC } (\%) = (\text{73} \pm \text{9}). \text{ WSR} \tag{9}$$

Equation (9) has R<sup>2</sup> = 0.90 and is highly significant (*p* < 0.0001).

**Figure 7.** The relationship between the percentage of villages in each Island Division with priority sanitation concerns and the sanitation type ratio, defined in Equation (2), from the 2006 and 2016 censuses. The results for Ongo Niua are highlighted.

Equations (5)–(9) suggest that for four of Tonga's IDs, village priority concerns over sanitation are related to the type of sanitation being used which is related to whether water is being sourced from rain tanks or piped water supply, irrespective of which census results are used. The exception is Ongo Niua. It is noted in Figure 7 that Ongo Niua had the largest reduction in STR of any ID between 2006 and 2016, so that sanitation may have been of lesser relative concern there. These results suggest that, with the exception of Ongo Niua, the census results for sanitation type or water source used for non-drinking purposes provide pointers to village priority concerns over sanitation at the ID level. The special case of Ongo Niua will be discussed in the following.

#### **4. Discussion**

#### *4.1. Information from Census Results*

Data on water consumed by different uses, particularly sanitation, is sparse in most SIDS, which results in donors relying on average values when planning interventions or emergency relief [33]. Here we have explored the sort of information that can be gleaned about water sanitation from available census results in the specific case of Tonga with its multi-island IDs. The census results (Table 1) show population is concentrated in the main ID Tongatapu, with over a third of the country's population in the capital area, Greater Nuku'alofa. Slightly less than a quarter of the population is scattered across Tonga's other four IDs with population densities lower in northern islands.

Between 2006 and 2016, Tonga's overall population declined slightly but with significant internal shifts in population from the northern and southern-most IDs to Tongatapu and to Greater Nuku'alofa (Figure 2). This increased pressure on water supply and sanitation in the main island. This shift from outer islands to population centers is widespread across PICs [35], and is driven largely by the availability of services, including improved water supply and sanitation services in population centers. In Tonga, natural disasters such as TC Ian [16] and earthquakes and tsunamis [36] also contribute to the population movement.

The census data shows a national shift in water sources for non-drinking purposes between 2006 and 2016. The minimal and declining use of household wells is positive because of the potential for contamination of groundwater by local sanitation systems [10]. There has been increased access to piped water supply and decreased rainwater use, which is valued for drinking, but the shift is uneven (Table 2, Figure 3). In Vava'u and Ha'apai, household access to piped water has hardly changed over the decade but household access to rainwater supply increased in those Divisions. Since this water is used for washing, bathing, and toilet flushing it represents a considerable strain on rainwater harvesting systems, especially during the May to October dry season [10,27]. Even well-managed rainwater systems in Ha'apai are expected to run dry about one year in nine, compared with one year in 28 in Tongatapu and Vava'u and one year in 45 in Ongo Niua [20].

The main types of household toilets in use in Tonga are cistern flush, pour flush, and pit toilets (Table 3). There are no statistics on the use of compost toilets despite an early trial in Ha'apai [37]. Nationally, there has been an increase in household use of cistern flush toilets between 2006 and 2016, a corresponding decrease in pour flush toilets and a large 50% decrease in pit toilets, which is fairly uniform across all IDs and Greater Nuku'alofa. The decrease in pit toilets is particularly important for reducing local groundwater contamination and improving hygiene.

The STR, defined in Equation (2), was introduced as an approximate relative measure of sanitation systems which use less water compared to those requiring more. STR halved in Tonga between 2006 and 2016 with decreases occurring in all IDs, and particularly Ongo Niua. This demonstrates a national shift to sanitation systems with larger water use. Despite this shift, the STR for Ha'apai and Ongo Niua in 2016 remain high compared to other IDs and particularly to Greater Nuku'alofa.

One of the questions this work sought to answer was: "Do census data show a link between island sanitation types and island water sources?" While there are many factors that influence the choice by households of the type of sanitation system [23], particularly in PICs, an adequate supply of water appears crucial. We found very strong and highly significant (*p* < 5.10−4) correlations between STR and WSR for all Tonga's IDs for both 2006 and 2016 census results (Equations (3) and (4)). This implies that, even in Tonga's outer islands, the move to improved sanitation systems is governed by access to adequate water supply. The change in STR revealed in the census data also implies that cistern flush toilets are the desired system by householders. The analysis of census data also showed continuing large differences in reliable water sources and improved sanitation systems available to households between the main island, Tongatapu including the capital region, Greater Nuku'alofa, and the other IDs.

One of the questions this work aimed to address was: "In the absence of detailed information, can census data be used to identify both improvements in sanitation and the diversity of sanitation

needs in PICs?" Comparison of the 2006 and 2016 censuses has shown marked changes in sanitation types used and revealed IDs which continue to be disadvantaged relative to the main island. We will now consider if these changes and differences are reflected in TSDFI and TSDFII.

#### *4.2. National Versus Local Sustainable Development Plans and Sanitation*

TSDFI, spanning the period 2011 to 2014, recognized explicitly the intimate link between water and sanitation evident in the census results. Of its nine national Outcome Objectives, two are directly relevant to water and sanitation. About 30% of the 27 Associated Strategies in TSDFI concerned infrastructure services, and 17% of them are focused on improving access to safe water and sanitation under the Infrastructure Outcome Objective. There are no water or sanitation Associated Strategies or related performance indicators under the Improved Health Outcome Objective. This is surprising in Tonga. All village water supply systems as well as national sanitation are the responsibility of the Ministry of Health.

TSDFII, covering the period 2015 to 2025, was built on lessons learnt through TSDPI but its structure is more complex and its objectives and strategies more numerous. TSDFII abandoned the linkage between water and sanitation in TSDFI. It contains no mention of water and/or sanitation in any of its 29 Organizational Outcomes. This is despite the fact that TSDFII claims it contributes to Tonga's commitments to SDG6. Of the 153 Strategic Concepts raised in the three-month consultations leading to TSDFII, one concerned water supply but, again, there was no mention of sanitation. This means that ministries have no national obligation to include sanitation in corporate plans or reports. This appears to imply that while water and sanitation were a priority in TSDFI, with the improvements in water supply and sanitation evidenced in the 2006 and 2016 censuses, water supply and sanitation are no longer national priorities in TSDFII, despite the continuing disparity between IDs evident in the censuses.

The available local village CDPs, presented in 2016, were developed over a nine-year period. Ha'apai had the highest median number of priority development concerns, perhaps partly reflecting the impacts of TC Ian in 2014 [16], while Ongo Niua had the lowest (Table 7). Sanitation was not ranked highest priority concern by any village in Tonga, and only 9% of villages ranked sanitation within their top three priorities, with women more concerned than men and both much more concerned than youth. Ha'apai villages had a much higher concern over sanitation than in Tongatapu which had the lowest concerns (Table 8). Nationally, 20% of villages identified sanitation within their list of development priorities (Figure 6). The percentage of villages expressing concern in Ha'apai (53%) about sanitation was an order of magnitude higher that in Tongatapu (5%). Nationally, again women had a higher concern over sanitation as a development priority than men or youth.

The results for sanitation are in contrast to the priority rankings for water supply in the CDPs where 55% of villages identified water supply as highest priority [20]. The lower priority for sanitation appears to stem from the fact that traditionally in PICs, sanitation was either a personal or household responsibility. There is no reticulated sewage system in Tonga. Piped water supply, however, is a community responsibility through Village Water Committees or, in population centers, the Tonga Water Board.

Sanitation priority development concerns expressed by IDs in their CDPs were strongly correlated with the sanitation type and water supply ratios from the census data, Equations (5)–(8), provided the results for Ongo Niua are ignored. This implies that the census results may be useful in identifying sanitation priorities in NSDS processes, certainly at the ID level. The apparent anomalous results in Ongo Niua appear to be due to major improvements in sanitation systems there between 2006 and 2016. Ongo Niua will be further discussed below.

Another of the questions this work sought to answer was: "Do top-down NSDS plans give the same weight to sanitation priorities as that identified in nation-wide bottom-up village development plans and is there an evolution of priorities in NSDS?" It has been shown here that while TSDFI did recognize water and sanitation as national priorities in line with the village CDPs, TSDFII did not. Suggested reasons for this discrepancy follow.

#### *4.3. Why is Ongo Niua an Outlier?*

Unlike other IDs in Tonga, the apparent lack of village concerns over sanitation in the CDPs of the remote northern Ongo Niua did not match the water and sanitation metrics in the 2006 and 2016 censuses. Ongo Niua ID is made up of three islands Niuatoputapu, Niuafo'ou, and Tafahi. Niuatoputapu has 57% of the population of Ongo Niua (1232 in 2016) while Tafahi has 2.5%. In Niuafo'ou, household water supplies are from rainwater harvesting [32] and sanitation is mainly provided by pit toilets and pour flush toilets. Niuatoputapu has a piped groundwater supply as well as household rain tanks and households access cistern flush toilets as well.

On 30 September 2009, Niuatoputapu island was struck by an 8.3 magnitude earthquake whose epicenter was 190 km northeast of the island. Three tsunami waves up to 17 m high struck the island, penetrating over one kilometer inland and inundated about 46 percent of the island. This resulted in the death of nine people, the complete destruction of one third of the houses and all government buildings, water supply and sanitation infrastructure [36].

A World Bank post-tsunami reconstruction project [36], completed in 2014, moved houses inland, constructed 73 new houses and a new piped water system, reconstructed roads, improved household rainwater harvesting systems, and installed pedestal cistern flush toilets and septic tanks. The project noted that there were still some pit and compost toilets on the island.

It appears that this reconstruction project is the reason that the STR in Ongo Niua decreased dramatically between 2006 and 2016 (Figure 4) and is probably the reason for the low ranking of sanitation in village CDPs in Ongo Niua. The 2009 tsunami, 2014 TC Ian, 2017 TC Gita, and 2020 TC Harold re-emphasize the vulnerability of sanitation and water supply infrastructure in SIDS to frequent natural disasters.

#### *4.4. The Mismatch between National and Local Development Planning for Sanitation*

Four possible explanations are advanced for the absence of priority given to water and sanitation in TSDFII in 2015 compared with the emphasis in TSDFI. The first is that the significant national improvements shown in sanitation and water supply in the 2016 census were recognized prior to the census being conducted in 2016 so that water and sanitation were no longer considered a priority for national planning. The second is that, traditionally, sanitation has been a household/individual responsibility, as in all PICs, and with no reticulated sewerage system in Tonga it is not considered government business, even though the government has to dispose of septage. This, however, does not explain that water and sanitation was a linked priority in TSDFI. The third is that all ministries and most of the government agencies with responsibility for TDSFII are located in Tongatapu and mostly in Greater Nuku'alofa where water supply is continuous and relatively plentiful and, as a consequence, improved cistern flush sanitation systems are widely in use. The fourth is that TDSFI was based on nine months of consultations in all IDs whereas TDSFII relied on consultations over three months in four of the five IDs.

#### *4.5. Sanitation in Islands Reliant on Rainwater Harvesting*

We found IDs with higher dependence on rainwater harvesting have generally more village-level concerns about the type of household sanitation system than in islands with greater access to piped water. The exception was Ongo Niua, where, in some islands, their volcanic geology means that groundwater appears absent or is very limited. Restricted rainwater storage, small roof areas, lack of maintenance, six month dry seasons, ENSO- and PDO-related droughts, and significant household demand mean most rainwater harvesting systems are not able to supply reliably sufficient water for flush toilets.

Several solutions have been trialed in small remote island countries and a range of zero or minimal water use systems are available [23]. Pit toilets do not use water and are relatively cheap, but they are regarded as less convenient and do pollute groundwater. Compost toilets were trialed in Lifuka in the Ha'apai ID [37], but they are not included in census surveys. CDPs coupled with census results show a general preference for flush toilets which are more convenient and require less upkeep than compost toilets. The use of seawater or brackish water for flushing has been used in high population density atolls either from reticulated supply systems or local wells. Leakage from saline reticulation systems can salinize fresh groundwater [10]. Desalinated water can also be used to provide water for flushing. However, desalination systems are expensive to operate and difficult to operate and maintain in remote outer islands [10].

While a number of economic, social, cultural, environmental, technical, and cultural factors influence the choice of household sanitation systems [23], we have shown here that an adequate supply of water is a major factor. Remote island communities look to the population centers and see flush toilets as the standard. Indeed, in Tonga, cistern flush toilets discharging into septic tanks are the desired goal. This is despite the fact the normal construction of septic tanks with concrete blocks inevitably leads to leakages with the potential to pollute soil and groundwater. Molded plastic septic tanks appear a safer but more expensive option [10].

#### *4.6. Sanitation, a Dilemma for Island Governments*

The dramatic change in emphasis on water and sanitation between TSDFI and TSDFII is evidence of a dilemma many PIC governments face. Water supply traditionally was the responsibility of the extended family, while sanitation was largely a personal matter which has evolved to a household responsibility. The transition to modernity in PICs has resulted in high density urban centers where water and sanitation are often government responsibilities but with lower density rural areas where tradition is often still strong. Addressing the diversity of needs in disparate situations equitably and responding to international programs and agreements such as SDG6, which focus on government responsibilities in sanitation, counter long-held traditional thinking.

In Tonga the situation is more complex. Most households prefer rainwater for drinking, even in the capital area, with government agencies or Village Water Committees supplying piped groundwater for other uses, where possible. Households, therefore, still play a role in water supply, which is more prominent in rural communities. Even in the capital and population centers, sanitation is a household responsibility with government responsible for collecting and disposing of septage in some areas. So, there is uncertainty about the appropriate role of government in sanitation as evidenced by its absence as a national priority from TSDFII. Clearly, implementing improved health, building, and environmental standards nationally are key government functions in sanitation and the facilitation of improved sanitation facilities through micro-financing schemes is a possibility [23]. Here we have shown that rural women are more concerned about sanitation than men or youth. Perhaps the election of more women to parliament would sharpen the national focus on sanitation?

#### *4.7. Limitations of this Work*

This work only examined aggregated ID level data for the census and CDP results. Both contain a wealth of information at the district and village level which could better inform both planning and intervention. We have not used here more sophisticated sanitation or WASH indices [21–23] to identify differences between IDs. This is due to the limited information available at the ID, district, and village level. Even per capita water consumption is not available except for the capital and population centers [27], and a handful of villages [30–32]. The recent passage of Tonga's Water Resources Act 2020 provides stimulus for improved data collection across the country.

The crude measures we have used here, WSR and STR, have inbuilt assumptions. The WSR assumes that all piped water systems in IDs are comparable. They are not. Greater Nuku'alofa and major centers in three other islands have access to a continuous supply of water, but in most rural villages piped water systems operate intermittently requiring household storage for continuous use. The STR assumes that flush toilets are what island communities desire irrespective of the adequacy of water supply. In the case of Ongo Niua, the large decrease in STR documented reconstruction efforts following a major natural disaster.

#### **5. Conclusions**

WASH has been identified as a major continuing national challenge in PICs [9] and improved governance is seen as a key step in addressing that challenge [14]. National sustainable development strategies and plans have been advocated as efficient governance instruments to identify overarching national priorities, select appropriate solutions, allocate responsibilities and resources, and fulfil international and regional commitments, especially in sustainable development. Inevitably, they are largely top-down processes. Transplanted governance institutions from one country may not suit another and standardized processes or formulaic approaches may not be apposite in PICs [6,20], particularly those with village communities dispersed over islands spread across large ocean and with a wide range of development challenges and traditional practices.

PICs have ideal strengths for bottom-up processes [7]. One of the inherent drawbacks of bottom-up processes is the inevitable time and cost penalties they incur. The Kingdom of Tonga provided the opportunity to examine how both top-down and bottom-up planning processes handle sanitation and water at the Island Division level. Consultations leading to TSDFII took three months, TSDFI took nine months, while the community consensuses building leading to CDPs evolved over nine years.

The previous two censuses in Tonga provide a clear picture of the household use of sanitation types and water sources, the changes in usage over time, and show large variations between the main island Tongatapu, especially in the capital area, and the other Island Divisions. The census data revealed that the type of sanitation system chosen is strongly correlated with access to piped water supply at the Island Division level. Censuses provide valuable data about differences in sanitation type and water sources which correlated well with aggregated village sanitation priorities in most Island Divisions. These relationships may also be evident in other PICs. The changes in sanitation metrics also revealed responses to natural disasters, so frequent in SIDS.

The first Tonga Strategic Development Framework, TDSFI, from 2011 to 2014 acknowledged the linkage between sanitation and water and their importance under an Infrastructure Outcome Objective. There is no recognition in the current TDSFII of that linkage and no mention of improved water and sanitation services under the Infrastructure Pillar or within the Health Outcome Objectives. The available bottom-up village CDPs show a markedly different set of priorities for water [20] and sanitation across Island Divisions, with the main Island Division being largely satisfied with the sanitation available while outer islands, and particularly Ha'apai, had significant development concerns over sanitation. One of the strengths of the CDP process was that it provided women and youth with the opportunity to voice their concerns as well as men who are normally the only group consulted. Overall, village CDPs showed higher concerns over sanitation by women than men with youth the least concerned.

A question raised here is: Can NSDS in multi-island countries be improved for sanitation and water outcomes? We have found here a major difference in the national priority given to sanitation and water in TSDFI and the diverse sanitation priorities expressed in village CDPs, especially by women, and their total absence in TSDFII. TSDFI reflects the sanitation data in the 2006 census. TSDFII does not acknowledge the large differences in sanitation systems evident in either the 2006 or 2016 censuses. Instead, TSDFII appears to reflect the lack of village priority concerns over sanitation found in village CDPs from the main island, Tongatapu.

Refining census questions to better target sanitation types and sources and reliability of water supply would assist NSDS processes. Synchronizing NSDS processes to follow and draw on the census data would allow the census results to be integrated into NSDS national priorities. Community development planning processes at the village level should be continuing processes, rather than a

one-off process, drawing on local strengths and run by the villages so that their results can be fed directly into NSDS. The advantage of TSDFI was that it had a less complex structure with objectives identifiable at the village level. A simple structure concentrating on island-relevant issues such as:

could be used as a template for village CDPs to feed directly into NSDS, with water and sanitation being covered under infrastructure, health, environment, and governance.

In the four years since their presentation in 2016, none of the priorities in CDPs had been analyzed until now. There is a pressing need for other identified priorities in the CDPs to be analyzed and incorporated into a revised TSDFII and updated ministry operational plans and reports. Without that, villagers will lose confidence in the relevance of both national and local planning processes.

We have had here the opportunity to analyze the priorities given to water and sanitation in top-down NSDSs and nation-wide, bottom-up village level Community Development Plans. The differences found here raise the question of whether NSDSs in other Pacific Island countries have the same mismatches and have to cope with similar differences between urban, rural and outer island development priorities.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2071-1050/12/22/9379/s1, Table S1: Sanitation Priorities in Community Development Plans, Tonga.

**Author Contributions:** Conceptualization, I.W., T.F. and T.K.; methodology, I.W., T.F. and T.K.; formal analysis, T.F. and I.W.; writing—original draft preparation, I.W.; writing—review and editing, I.W., T.F. and T.K.; project administration, T.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** This work arose as a result of a strategic planning project supported by the World Meteorology Organization under its Climate Risk and Early Warning Systems Initiative for Pacific Island Countries focusing on improved governance. WMO Pacific are thanked for that support. We are grateful to Karin Nagorcka for editorial assistance. The authors thank an unnamed reviewer whose comments improved this paper.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

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