Water Resources


Category Description

Effective wastewater management is essential to human and ecosystem health. Untreated wastewater contaminates rivers, lakes, and oceans. It spreads diseases that kill millions of people each year. Ecosystem impacts from wastewater range from eutrophication to increased water temperature, depending on the wastewater source. Wastewater pollution threatens ecosystem vitality and clean water resources in all countries, but the need for wastewater management is especially pressing in countries facing water scarcity. Growing populations also threatens the ability of some countries to ensure clean fresh water resources. Connecting people to adequate wastewater collection and treatment systems mitigates these damages by preventing pollution and making treated water available for re-use.

Indicator included

1.     Wastewater treatment: We measure wastewater treatment as the percentage of wastewater that undergoes at least primary treatment in each country, normalized by the proportion of the population connected to a municipal wastewater collection system.

Countries can minimize the negative environmental impacts of sewage by treating wastewater. Water treatment can remove pathogenic microorganisms and other harmful pollutants, minimizing health risks to humans and ecosystems. Maximizing wastewater treatment is an effective way to assess the cleanliness of each country’s water resources. Our wastewater treatment indicator captures only water treatment by centralized municipal utilities, as global data from independent water treatment such as private septic systems are lacking. 

Water Resources Indicator
Wastewater treatment %

Category Overview

Clean water is essential for all life. In many countries, the lack of wastewater treatment poses a major threat to clean water resources. Wastewater refers to polluted water that is unfit for drinking, irrigation, or other useful purposes (Malik, Hsu, Johnson, & de Sherbinin, 2015). Approximately 80% of all wastewater produced globally is discharged into the environment untreated (United Nations World Water Assessment Programme, 2017). Untreated wastewater threatens human life, human livelihoods, and ecosystem health.

Many human activities pollute water systems. The pollutants contained in wastewater vary depending on their source. These different pollutants dictate the health impacts of untreated wastewater. Major sources of wastewater include domestic water use, agriculture, industrial activities, and groundwater runoff. Domestic wastewater, or sewage, contains organic materials that can carry pathogenic microorganisms. Sewage can also contain pharmaceutical drugs and other chemicals that are commonly disposed through household toilets and sinks. Agricultural wastewater often carries excess nutrients from fertilizer, pesticide residues, and growth hormones used on livestock. Industrial wastewater can contain hazardous chemicals, metals, or excess heat. Groundwater runoff picks up surface pollutants, ranging from plastics and oil in urban areas, to concentrated hazardous metals and chemicals from dumps (World Water Assessment Programme & UNESCO, 2017). While the impacts of wastewater pollution vary by source, all untreated wastewater harms human and ecosystem health.

Managing and treating wastewater can be complex and expensive. Collection infrastructure must respond quickly to environmental pressures. Storms and flooding, for example, can overwhelm wastewater treatment infrastructure and cause untreated wastewater to overflow directly into the environment. Preventing overflow events challenges wastewater management planning in wealthy and developing countries (World Water Assessment Programme & UNESCO, 2017). Wastewater treatment is often classified in progressively more effective and expensive tiers. Primary treatment simply filters suspended organic solids, and wastewater treated in this way is not typically potable. More advanced secondary and tertiary treatment ensures higher water purity (Malik et al., 2015).   

Wastewater collection and treatment data can help countries develop and justify policies designed to protect water resources. A 2004 World Health Organization report found that wastewater treatment and disposal costs are small compared to damages from untreated wastewater (Hutton & Haller, 2004). Expanding and standardizing data collection can help clarify the economic argument for expanding treatment infrastructure, and support other policies and innovations that improve wastewater management (Mateo-Sagasta, Thebo, & Raschid-Sally, 2015). Gathering such data is logistically complex, especially in rural areas where collection and treatment is often distributed. City-level data is therefore more common than country-level data (Malik et al., 2015).

Clean water is essential for environmental, economic, and social wellbeing. In 2010, the United Nations (UN) formally acknowledged that clean water and sanitation are necessary for the realization of all basic human rights. The 2015 Sustainable Development Goals (SDGs) and their predecessor, the Millennium Development Goals (MDGs), emphasize the importance of clean water in sustainable development. Both note the global threats to water quality and availability posed by rising demand for water, increased pollution, and greater wastewater generation. Wastewater treatment can alleviate many of these problems.

Environmental: Pollution from untreated wastewater causes many environmental problems. Pollutants that are toxic or that reduce oxygen levels in water can kill aquatic species and dramatically disturb ecosystems. Decaying organic matter from domestic and municipal sources captures dissolved oxygen. High concentrations of phosphorous and nitrogen from agricultural fertilizer also create oxygen poor environments through eutrophication. Metals, salts, and pesticides create a host of problems including toxicity for animals and plants (World Water Assessment Programme & UNESCO, 2017).

Treated wastewater can also harm ecosystems. Basic wastewater treatment filters out suspended solids and organic matter, but does not remove all pollutants. Wastewater that is recycled for irrigation can lead to soil salinization, as salts remaining in the treated wastewater accumulate and gradually prevent proper water adsorption by crops (Welle & Mauter, 2017). ‘Emerging pollutants’ including pharmaceutical drugs and contraceptives are often difficult to remove, even with tertiary treatment. Small concentrations of these pollutants have been found to disrupt hormonal processes in animals, causing birth defects and cancers, among other health problems (World Water Assessment Programme & UNESCO, 2017).

Social: Pathogens that pollute drinking water pose multiple threats to human health (Environment and Climate Change Canada, 2014). Diseases associated with poor water and sanitation include cholera, dysentery, typhoid, and polio. Around 1.8 billion people use a source of drinking water that is contaminated with fecal coliforms (United Nations Water, n.d.-b). Worldwide, approximately 1.3 million people die each year from diarrheal diseases. Poor hygiene and unsafe water are major contributors to these deaths (GBD Diarrhoeal Diseases Collaborators, 2017).

Women and children in developing countries are most affected by unsafe management of human waste (World Water Assessment Programme & UNESCO, 2017). Water and sanitation-related diseases remain among the major causes of death globally in children under five years of age (United Nations, n.d.). Women and children in many countries bear primary responsibility for managing household water supply, sanitation, and health. This includes collecting water, which is a time consuming, difficult, and sometimes dangerous task for women and girls. These responsibilities can compromise school participation, health and disease management, and other components of a safe, productive, and healthy life (United Nations Water, n.d.-a).

Economic: In 2004, the World Health Organization published a cost-benefit evaluation of water and sanitation service options for 17 WHO sub-regions in Europe, Africa, and Asia. These sub-regions cover over 55% of the global population. The study found that, for all water and sanitation improvement options, health benefits outweighed implementation costs. The estimated return to society ranged from US$5 to US$28 for every US$1 spent on sanitation, depending on the region (Hutton & Haller, 2004). The global average is US$5.5 per US$1 spent (World Water Assessment Programme & UNESCO, 2017). Economic benefits from water and sanitation improvements include a decrease in illness, medical treatment, and death rates by diarrheal disease, as well as better water resource management for agriculture and aquatic- and marine-derived food sources.

Global Impact

Several UN SDG goals and targets relate to wastewater management, demonstrating the broad importance of clean water resources to global sustainable development.

Goal 6: Ensure availability and sustainable management of water and sanitation for all.

Goal 2, Target 4: By 2030, end all forms of malnutrition, including achieving, by 2025, the internationally agreed targets on stunting and wasting in children under 5 years of age, and address the nutritional needs of adolescent girls, pregnant and lactating women and older persons. 

Goal 3, Target 3: By 2030, end the epidemics of AIDS, tuberculosis, malaria and neglected tropical diseases and combat hepatitis, water-borne diseases and other communicable diseases.

Goal 3, Target 9: By 2030, substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination.

Goal 9, Target 1: Develop quality, reliable, sustainable and resilient infrastructure, including regional and transborder infrastructure, to support economic development and human well-being, with a focus on affordable and equitable access for all.  

Goal 9, Target A: Facilitate sustainable and resilient infrastructure development in developing countries through enhanced financial, technological and technical support to African countries, least developed countries, landlocked developing countries and small island developing States.

Goal 12, Target 4: By 2020, achieve the environmentally sound management of chemicals and all wastes throughout their life cycle, in accordance with agreed international frameworks, and significantly reduce their release to air, water and soil in order to minimize their adverse impacts on human health and the environment.

International Organizations

International Water Association (IWA): IWA organizes events and projects that connect professionals working on solutions for water and wastewater management. The NGO aims to place water on the global political agenda and to influence best practices in regulation and policy making. http://www.iwa-network.org/.

International Water Resources Association (IWRA): IRWA aims to spread information and best practices about water resources management. The NGO organizes international water conferences to connect scientists with policymakers. http://www.iwra.org/.  

United Nations Children’s Fund (UNICEF): UNICEF’s water, sanitation, and hygiene team works in over 100 countries to improve water treatment services for children and their families. https://www.unicef.org/wash/.

United Nations Framework Convention on Climate Change (UNFCCC): UNFCCC organizes studies on water resource management best practices. http://www4.unfccc.int/sites/NWP/Pages/water-page.aspx.  

United Nations Water (UN-Water): UN-Water coordinates the water-related activities of more than 30 UN organizations and other international groups. http://www.unwater.org/.

Multilateral Efforts

23rd Conference of the Parties: COP 22 and COP 23 have included an “Action Day for Water,” during which international organizations have made concrete recommendations for climate change adaptation projects and financing related to water quality (United Nations, 2016).

UN Interagency and Expert Group on Sustainable Development Goal Indicators (IAEG-SDG): In March 2017, the 5th meeting of the IAEG-SDG recognized the need to reduce countries’ reporting burden through data sharing and open access.

UN World Toilet Day: Raises awareness and inspires action to tackle the global sanitation crisis, which requires both access to toilets and solutions for connecting and treating wastewater for sustainable development. http://www.un.org/en/events/toiletday/.

UN-Water Webinars: will convene webinars and in-country discussions on national focal points in approximately 50 countries to introduce SDG 6 monitoring methodology and implementation. Each country is expected to produce baseline data by September 2017 in preparation for the High-Level Political Forum on Sustainable Development’s review of SDG 6 in 2018 (United Nations Water, 2017).

World Water Week: The annual event addresses the theme “water and waste – reduce and reuse.” The most recent event was held during August 2017 in Stockholm, Sweden. http://www.worldwaterweek.org/.


Ideally, a wastewater treatment indicator would capture the percentage of all wastewater that is treated within each country. Such an indicator would require the volumes and locations of wastewater generation and collection from all sources. This ideal indicator would also require data showing the volume of wastewater that is treated by utilities and by distributed treatment systems. Limited wastewater generation and collection data make construction of the ideal indicator impossible, as do limited data on distributed treatment systems. Malik et al. (2015) describe an ideal wastewater indicator considering data limitations. This indicator would be constructed to show the volume of wastewater collected and treated by within each country, normalized by the population served by each utility (Malik et al., 2015).

Regular wastewater treatment data collection and reporting would support the realization of SDGs related to clean water resources. Unfortunately, national and municipal data collection for wastewater generation, collection, and treatment are sometimes unavailable and rarely updated regularly. The most robust data include basic information about connections to wastewater collection or treatment. Countries that collect data typically focus on centralized municipal utility treatment, which is easier to collect than data on distributed rural wastewater treatment. Some cities collect detailed wastewater generation and treatment data. This data can support the indicator proposed by Malik et al. (2015), but not an indicator that captures water treatment in rural areas. Countries and cities that do collect data make infrequent updates, and tracking progress across time is difficult. Developing countries tend to update data less frequently than developing countries, but France and Australia are examples of developed countries that do not have recent wastewater treatment data (Malik et al., 2015).

Further difficulty arises from attempts to standardize monitoring approaches for cross-country comparisons. Global data sharing is poor, and access to original data sources is frequently lost in data aggregation (Hering, 2017). Several UN agencies are cooperating to develop a new global monitoring initiative, the Integrated Monitoring of Water and Sanitation Related SDG Targets (GEMI). This initiative aims to synchronize and expand existing monitoring efforts on wastewater treatment.

Given limitations in wastewater treatment data collection and reporting, the water resources indicator developed by Malik et al. (2015) for the 2014 EPI is the best measure to compare global wastewater treatment.

Indicator Background

Malik et al. (2015) provide the first global wastewater treatment indicator, which uses municipal utility collection as a proxy for national collection.

The 2018 EPI uses the wastewater indicator introduced first in the 2014 EPI. This indicator measures the percentage of wastewater from sources connected to a centralized treatment system that is treated. This percentage is calculated by multiplying two proportions: the wastewater treatment level in each country, and the connection rate. The wastewater treatment level is the amount of wastewater that is treated, divided by the total amount of wastewater generated. The connection rate is the number of people within the country that are connected to a sewer system, divided by the total population of the country (Malik et al., 2015).

Data Description

Most data in the EPI wastewater collection and treatment dataset are compiled from four sources: the UN Statistics Division (UNSD), the Organisation for Economic Cooperation and Development (OECD), the Pinsent Masons Water Yearbook, and UN Food and Agriculture Organization’s (FAO) Aquastat system. EPI supplements these sources with data from publically available and country-specific reports to form a more comprehensive dataset. In cases where national-level data are unavailable, data are gathered from cities and utilities. In total, the EPI dataset includes information about wastewater treatment and sewer system connections for 176 countries.


The 2018 EPI wastewater treatment indicator reveals data limitations, and can inform future data collection and reporting to support more robust metrics. There are many limitations to international wastewater data. Available datasets are infrequently updated. As a result, new values for the 2018 EPI were only available for a handful of countries. Data from different sources occasionally have different values for the same country, indicating differences in definitions or methods. Where national level data is unavailable, municipal data sources are used to extrapolate national values. This data may not be representative of a country’s overall wastewater treatment rate, as important wastewater sources such as agriculture and industrial plants can be located in rural areas (Malik et al., 2015). Most datasets do not distinguish simple filtration from more intensive wastewater treatment. Detailed information about the level of wastewater treatment is available from some developed countries, but such information is not common enough to create an indicator that compares the treatment level across countries. Greater international attention is needed to provide standardized, accurate, detailed, and frequent data on protection of water resources.


Global Trends

Ensuring clean water resources is an important measure of a country’s environmental performance. As demand for water from agriculture, industry, and residential users increases, countries will need to collect and treat wastewater to prevent pollution from harming human and ecosystem health. Our results reflect the preliminary assessment of global wastewater treatment conducted by Malik et al. (2015). Some countries score well on wastewater treatment, but there is room for improvement across all countries and regions.

Table 13-1. Global trends in managing Water Resources.
Note: For most EPI indicators, Current refers to the most recently available data, and Baseline refers to historic data approximately ten years previous to Current. For the wastewater treatment indicator, Baseline and Current data are the same due to lack of regularly updated datasets.
Indicator Metric Score
  Baseline Current Baseline Current
Wastewater Treatment 62.1% 62.1% N/A 62.13

Due to unavailability of global wastewater treatment data, the global performance in wastewater treatment has not changed from the baseline. Data quality is especially poor in Latin America and the Caribbean. 82.2% of countries in this region lack recent wastewater data. Europe has the best data of any region, with 31.7% of countries missing recent data (Malik et al., 2015). Improving wastewater treatment data collection and reporting is an essential step in moving the world toward 100% wastewater treatment. Countries may begin to improve wastewater treatment data quality and performance in response to the UN SDG 6, which targets global reduction in untreated wastewater.

Leaders & Laggards

While most countries can improve their wastewater treatment performance, some countries score very highly in the Water Resources category. All leading countries are wealthy, and most are threatened by water scarcity. Strong policies in the European Union, Singapore, and Israel have also encouraged high performance in wastewater treatment.

Table 13-2. Leaders in Managing Water Resources.
Rank Country Score
1 Malta 100
1 Singapore 100
3 Netherlands 99.90
4 United Kingdom 99.82
5 Luxembourg 99.76
6 Spain 99.71
7 Switzerland 99.67
8 Germany 99.65
9 Israel 99.49
10 Australia 99.44

All of the top ten countries in the Water Resources category are relatively wealthy. According to the World Bank, each leading country in Table 13–2 ranks within the top third globally in GDP per capita (World Bank, 2016). This result is expected, as wastewater treatment rates are typically higher in developed countries. Wealthier countries also use advanced treatment for a higher percentage of wastewater (World Water Assessment Programme & UNESCO, 2017).

Most leading countries also experience water stress. Water stressed nations have high incentive to treat and recycle wastewater.  According to WRI Aqueduct, seven of the countries in Table 13–2 will experience medium to high water stress under a business-as-usual scenario by 2020 (WRI Aqueduct, 2015). This scenario places Singapore and Israel in the top ten water stressed countries globally. Germany, Netherlands, and Switzerland are the only leaders that are not expected to experience medium to high water stress (WRI Aqueduct, 2015).

In the European Union, the Urban Waste Water Treatment Directive requires member states to report performance on wastewater collection and treatment. This Directive tracks collection rates, secondary treatment rates, and more stringent treatment rates. Compliance rates with the Directive vary between member states. Most EU countries that rank within the top ten for the 2018 EPI fully comply with the Directive. Malta is a notable exception. While Malta has wastewater treatment infrastructure in place, the country’s water quality is threatened by discharges of agricultural waste and high concentrations of salt in sewage (European Commission, 2017). These problems are not captured by wastewater treatment indicator. Future version of the EPI may capture more detailed variations in performance including the level of treatment applied in each country. 

There are 38 countries with a score of zero. All are developing countries in Africa, Asia, Eastern Europe, and Central and South America. Countries with zero scores have available data, but Malik et al. (2015) indicate difficulty finding good wastewater treatment and connection values for some of these countries. In some cases, national values are extrapolated from city level data. Other cases required interpreting anecdotal or qualitative descriptions of wastewater treatment. As an example, the wastewater connection value for Guyana interpreted from water utility report, which states that “there are no treatment processes” in the capital city (Malik et al., 2015). This qualitative statement gives Guyana a score of 0.

Water resources are threatened in many Sub-Saharan African countries. Ethiopia receives a 0 score for wastewater treatment in the 2018 EPI, and faces many of the pressures common to the region. In Sub-Saharan Africa, urban populations are growing more rapidly than in any other region globally. Addis Ababa has struggled to connect growing populations to wastewater treatment. While treatment infrastructure exists, treatment plants in the city are under-capacity due to lack of municipal wastewater connections. A 2009 study found that in one area of the city, less than 3% of wastewater reached a treatment facility (World Water Assessment Programme & UNESCO, 2017). Connecting households and businesses to wastewater treatment in growing cities is a financial and logistical challenge, but is important to maintain human and ecosystem health. 

Box 13-1. Framing Wastewater as a Resource, not a Waste

In addition to protecting human and ecosystem health, wastewater treatment can be used to recover valuable resources. Wastewater holds a potentially high value as an unconventional water resource in water stressed regions (United Nations, n.d.). Singapore’s NEWater program is a successful example of wastewater recycling. Household wastewater in Singapore is collected and treated using intensive processes that remove living organisms and other contaminants. The recycled water is then used in industrial processes. Although the recycled water is potable, NEWater supplies only a small percentage of Singapore’s drinking water supply. Public fears over the safety of recycled wastewater have prevented wider use in the municipal water supply. Singapore is attempting to change public perception through education campaigns (United Nations World Water Assessment Programme, 2017).

Properly managed wastewater can be a source of nutrients, energy via anaerobic digestion of organic material into methane, and even high-value by-product recovery like metals (Asano, 1998). Some companies use heat from wastewater to drive industrial processes. The trend toward wastewater recycling and resource recovery was demonstrated on World Water Day 2017, when UNESCO released its annual World Water Development Report, focusing on wastewater as an untapped resource (United Nations World Water Assessment Programme, 2017).

Understanding wastewater as a resource instead of a burden is still uncommon. To increase demand for wastewater recycling and resource recovery, countries must develop flexible regulatory and institutional frameworks and provide funding for new or modified wastewater treatment infrastructure. Status quo regulatory frameworks consider wastewater a pollutant to be minimized, and new rules are needed to accommodate the range of potential applications (Drechsel, Qadir, & Wichelns, 2015). Advanced treatment for wastewater reuse is capital-intensive, but nutrient recovery can add significant new value streams to the treatment process (Rao, Drechsel, Hanjra, & Danso, 2015). Certain wastewater treatment technologies, like anaerobic digestion, can reduce or even neutralize wastewater treatment’s energy burden (Lazarova, Asano, Bahri, & Anderson, 2013). Wastewater is not merely a collect-and-treat problem. Rather, wastewater can be a valuable resource providing sustainable opportunities for water, nutrient, and energy recovery.


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