Wastewater reuse: which countries are leading the way?
Faced with a global water shortage, wastewater reuse is the way of the future.
Julie Mendret, University of Montpellier
Once treated, wastewater can be used for a variety of purposes: irrigation of green spaces and crops, fire-fighting, road washing and groundwater recharge.
Some countries or states - such as Australia, California, Cyprus, Spain, Florida, Israel, Jordan, Malta and Singapore - have set themselves the target of meeting between 10% and 60% of their water needs by reusing treated wastewater.
The ubiquitous nature of wastewater means that it can be treated throughout the world, unlike desalination, another solution to water shortages, which is confined to coastal areas and consumes a lot of energy.
France lags behind
In France, "reuse" remains underdeveloped. This is due to a lack of public awareness and strict regulations. Within the European Union, the May 21, 1991 directive stipulates that "waste water shall be reused where appropriate". Each European country therefore has its own regulations on wastewater reuse.
France has thus defined the qualities required for the reuse of treated wastewater to irrigate crops or green spaces. Industry professionals are campaigning for a relaxation of the law, which frames wastewater reuse too strictly, above all for health reasons. The European Commission has recently taken up this issue and in 2018 issued a proposal for regulations dedicated to agricultural irrigation with the aim of facilitating the reuse of treated wastewater.
Depending on the local regulatory context, wastewater reuse is experiencing uneven development worldwide.
In recent decades, a number of developed countries suffering from severe drought have turned to wastewater reuse: the southern United States (California, Florida, Texas, Arizona, for example), Australia, Singapore, Israel and the countries of the Persian Gulf. The State of California, a pioneer in wastewater reuse, introduced the first regulations in this field at the beginning of the twentieth century. Since then, these regulations have evolved, with ever more advanced treatments to guarantee top-quality water, and many countries have drawn inspiration from them.
In Europe, water requirements differ between North and South: wastewater reuse practices are more widespread in southern countries. In some cases, however, as in Greece and Italy, overly strict regulations are holding back this use, as they entail excessively high costs for monitoring water quality(74 parameters to be monitored under Greek regulations). In Spain, the most active European country in this field, over 150 reuse projects have been implemented in recent years.
A delicate assessment
While over sixty countries worldwide practice wastewater reuse, it is difficult to identify which ones reuse the largest volumes, due to a lack of standardized data.
Based on available data, and considering annual volumes, China, Mexico and the United States are the countries that reuse the largest quantities, but the first two mentioned produce water of poor quality linked to an insufficient level of treatment.
In terms of water reuse per capita, Qatar, Israel and Kuwait rank highest. Kuwait, Israel and Singapore rank first if the criterion considered concerns the percentage of water reused in relation to the total amount of water used. Finally, in terms of technological advances, California, Singapore and Japan are probably the most innovative countries.
The Singapore reference
Singapore is a world-renowned reference in this field. With a very high population density, this island of 699 km2 was faced with a growing water shortage and turned to the reuse of wastewater after a state-of-the-art treatment process combining microfiltration, reverse osmosis and UV radiation.
This water, known as "Newater", is used for industrial applications and in cooling towers, but a fraction is also mixed with natural water and fed into the drinking water network. Such examples of direct reuse for drinking water treatment are rare, mainly due to psychological barriers.
The Windhoeck wastewater treatment plant in Namibia is the only example of direct reuse for drinking water treatment on a large scale (21,000m3/day).
Major obstacles
As we can see, while wastewater reuse is a solution for the future, it suffers from a problem of social acceptability: a recent survey in Kuwait showed that the two main fears about "reuse" for domestic use were health risks (69%) and an aversion to such use (44%).
In addition, its application for more or less restrictive uses, such as irrigation, groundwater recharge or direct consumption, could be limited by the quality of the water in question. Indeed, the major drawbacks of these waters are their high salinity, which can adversely affect agricultural productivity and soil quality; and the presence of emerging pollutants, known as "micropollutants", identified as endocrine disruptors.
However, in France and abroad, water treatment research laboratories are actively working on the development of new, innovative processes, based in particular on the combining physical and chemical treatments that will ensure water quality suitable for the intended uses.
Julie Mendret, Senior Lecturer, HDR, University of Montpellier
This article is republished from The Conversation under a Creative Commons license. Read theoriginal article.