Use of Treated Wastewater Could Reduce Freshwater Demand: UNU-Backed Study


  • 2013•09•10     Hamilton

    Amid growing competition for freshwater from industry and cities, the first-ever international study on the availability of data about wastewater generation, treatment and use predicts that there will be a rapid increase in the use of treated wastewater for farming and other uses worldwide.

    The study, led by the UNU Institute for Water, Environment and Health (UNU-INWEH, Canada) and Tottori University (Japan), found that treated wastewater remains mostly unused and, in many nations, is its usage is not even quantified.

    Of 181 countries studied, only 55 have information on three key aspects of wastewater: generation, treatment and reuse. While another 69 countries have data on one or two of those aspects, 57 countries have no information. And where data does exist, it is mostly outdated; some 63% of the data is at least five years old.

    The study — “Global, Regional, and Country-level Need for Data on Wastewater Generation, Treatment, and Use” — published in the Elsevier journal Agricultural Water Management (vol. 130, Dec. 2013), found that as water supplies fall and stress rises in many areas, the potential of wastewater as a resource is being widely recognized. Water demands already exceed supplies in regions with more than 40% of the world’s population, and in 12 years the spectre of water scarcity could confront up to 60% of the world population.

    Synthesizing what data exists on wastewater treatment, the study found that, on average, high-income countries treat 70% of their generated wastewater. Upper-middle-income and lower-middle-income countries treat 38% and 28% of their generated wastewater, respectively, while lower-middle-income countries treat just 8%.

    In North America, of the estimated 85 cubic kilometers (85 trillion litres) of wastewater generated each year, about 75% is treated. Only 3.8% of that treated wastewater is used, however.

    “From the earliest of times, most wastewater has truly been wasted. However, it is a vast resource if we reclaim it properly, which includes the separation of municipal from industrial wastewater”, said UNU-INWEH Director Zafar Adeel.

    In developing countries — particularly in water-scarce countries — wastewater volumes are thought to have increased substantially in recent years, due in part to rural–urban migration.

    Many farmers in water-scarce developing countries irrigate with (often untreated) wastewater because:

    • it is the only water source available for irrigation year-round,
    • wastewater irrigation reduces the need for purchasing fertilizer, and
    • wastewater irrigation involves less energy cost if the alternative clean water source is deep groundwater.

    Wastewater irrigation enables farmers in peri-urban areas to produce high-value vegetables for sale in local markets.


    “Given the growing importance of wastewater management to the health of people and economies at local and national levels, having up-to-date basic insights into wastewater generation, treatment and reuse is an essential investment”, said study lead author Toshio Sato of Tottori University.

    “The key point underlined throughout this report”, added UNU-INWEH author Manzoor Qadir, “is the need to invest the time and resources to fill the global data gap”. 

    The study suggests that irrigation with treated wastewater likely will expand in developed countries, particularly in arid and semi-arid areas, where competition for freshwater supplies will continue to increase. Technical solutions and public policies generally are adequate in developed countries to accommodate increases in the treatment and use of wastewater.

    The same is not true for many developing countries, where treatment facilities already are inadequate and much of the wastewater used by farmers is not treated. It is likely that the demand for wastewater as a source of irrigation water will increase in arid and semi-arid areas of developing countries at a faster pace than the development of technical solutions and institutions that might ensure the safe distribution and management of wastewater.

    Thus, the key technical and policy questions in developing countries include those pertaining to:

    • better methods for handling untreated wastewater on farms and in farm communities,
    • better recommendations regarding the crops and cultural practices most suitable for settings in which wastewater is the primary source of irrigation,
    • better methods for protecting farm workers and consumers from the potentially harmful pathogens and chemicals in wastewater, and
    • capacity development of relevant professionals to tackle the complex issues arising from the agricultural use of wastewater.

    According to the study, on which UNU-IWEH and Tottori University collaborated with the International Center for Agricultural Research in the Dry Areas (Syria), International Water Management Institute (Sri Lanka) and Hazara University (Pakistan): “The country-level information aggregated at the regional and global levels would help in identifying the gaps in pertinent data availability and assessing the potential of wastewater in food, feed and fish production at different scales. Better data will enable the research and policy community to enhance understanding and craft effective solutions that will benefit millions of producers and consumers, worldwide.”

    For more information about the study, see World Lacks Data on Wastewater Reuse on the UNU-INWEH website, or read the UNU-INWEH press release.