Water is essential for human survival and well-being and plays an important role in many sectors of the economy. However, water resources are irregularly distributed over space and time, and they are under pressure due to human activity and economic development (Forslund et al., 2009).
Accelerated urbanization and the expansion of municipal water supply and sanitation systems also contribute to the rising demand (UN, 2017a). Furthermore, climate change scenarios project spatial and temporal variations of water cycle dynamics, which exacerbate the discrepancies between water supply and demand (Evans, 1996; UN, 2017a).
Water for irrigation and food production constitutes one of the greatest pressures on freshwater resources, with agriculture accounting for over 70 percent of global freshwater withdrawals and up to 90 percent in some fast-growing economies (UN, 2017a). Projections for biofuel production indicate that if by 2030, 5 percent of road transport is powered by biofuels (the EU target is 10 percent by 2020 (European Commission, 2009)), this would amount to at least 20 percent of the water used for agriculture globally (Comprehensive Assessment of Water Management in Agriculture, 2007). Industry is also a major water user, accounting for between 10 per percent (Asia) and 57 percent (Europe) of total water consumption (FAO, 2012). Water (availability/scarcity/management) is one of the top global risks, according to a World Economic Forum Global Risk Report (2015), estimating a 40 percent shortfall in water supply globally by 2030 if no changes are made in how water is managed.
As freshwater supplies become more limited, and economic development comes with increasing water demand, technologies such as desalination and water re-use are often recognized as solutions with great potential in reducing the gap between availability and demand (IWA, 2015). However, on a larger scale, brine released from desalination plants includes chemical residues that negatively affect coastal ecosystems (Dawoud and Al Mulla, 2012). Furthermore, although desalination may solve the problem of water scarcity in water-stressed areas, the problem of associated wastewater management and the costs involved still persist (IWA, 2015). Continued failure to address wastewater as a major social and environmental problem would also compromise other efforts towards achieving the 2030 Agenda for Sustainable Development (UN, 2017b).
The ability to reuse water, regardless of whether the intent is to augment water supplies or manage nutrients in treated effluents (also a factor leading to water reuse), has positive benefits that are also the key motivators for implementing reuse programs (EPA, 2012). These benefits include improved agricultural production; reduced energy consumption associated with production, treatment, and distribution of water; and significant environmental benefits, such as reduced nutrient loads to receiving waters due to reuse of the treated wastewater (Fatta-Kassinos and Dionysiou, 2016). In Europe, the implementation of the Urban Waste Water Treatment Directive (91-271-EEC) has already helped to obtain treated wastewaters of quite high quality that could be reused for certain applications or improved by polishing steps for uses with higher quality requirements (European Commission, 2001).
Recycling and reuse are central to a circular economy approach and can offer strategies to improve water supply by managing wastewater better. Water reuse has many applications in general, but particular techniques or levels depend on local priorities and possibilities and economic feasibility. It is most appropriate in areas where there are extreme water shortages, high water costs, and high technical capabilities. Generally, high levels of technical management, monitoring, and regulatory skills are needed for recycling and reuse to be both safe and effective. Water reuse faces numerous barriers, ranging from public perception to pricing and regulatory challenges that could be addressed more effectively through a wider circular economy perspective. Water reuse could be promoted through policy instruments such as charges and tariffs, increasing its cost-effectiveness and acceptability, as part of a transition to a circular economy.
These findings are described in the article entitled Water Reuse from a Circular Economy Perspective and Potential Risks from an Unregulated Approach, recently published in the journal Current Opinion in Environmental Science & Health. This work was conducted by N. Voulvoulis from Imperial College London.
- Comprehensive Assessment of Water Management in Agriculture (2007) Water for Food, Water for Life: A Comprehensive Assessment of Water Management in Agriculture. London/Colombo, Earthscan/International Water Management Institute.
- Dawoud, M.A. and Al Mulla, M.M. (2012) Environmental Impacts of Seawater Desalination: Arabian Gulf Case Study. International Journal of Environment and Sustainability, 1 (3), p. 22‐37.
- EPA (2012) 2012 Guidelines for Water Reuse.
- European Commission (2001) Pollutants in urban waste water and sewage sludge.
- European Commission (2009) DIRECTIVE 2009/28/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL on the promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC.
- Evans T.E. (1996) The effects of changes in the world hydrological cycle on availability of water resources. In: Global climate change and agricultural production. Direct and indirect effects of changing hydrological, pedological and plant physiological processes, John Wiley & Sons Ltd., Chistester, England.
- FAO (2012) Irrigation water requirement and water withdrawal by country. FAO AQUASTAT Reports.
- Fatta-Kassinos, D. and Dionysiou, D.D. (2016) Advanced Treatment Technologies for Urban Wastewater Reuse (The Handbook of Environmental Chemistry). Springer.
- Forslund, A., Malm Renöfält, B., Barchiesi, S., Cross, K., Davidson, S., Ferrel, T., Korsgaard, L., Krchnak, K., McClain, M., Meijer, K., Smith, M. (2009) Securing Water for Ecosystems and Human Well-being: The Importance of Environmental Flows. Swedish Water House Report 24.
- IWA (2015) Alternative Water Resources: A Review of Concepts, Solutions and Experiences.
- UN (2017a) The United Nations World Water Development Report 2017.
- UN (2017b) Wastewater: The Untapped Resource. The United Nations World Water Development Report 2017.
- World Economic Forum (2015) Global Risks 2015.