Wastewater reuse: which countries are leading the way?
F aced with a global water shortage, wastewater reuse is a promising solution for the future.
Julie Mendret, University of Montpellier
Once treated, wastewater can be used for a variety of purposes: irrigating green spaces or crops, fighting fires, washing roads, or even replenishing groundwater reserves.
Some countries or states—such as Australia, California, Cyprus, Spain, Florida, Israel, Jordan, Malta, and Singapore—aim to meet 10 to 60% of their water needs through the reuse of treated wastewater.
The ubiquity of wastewater means that it can be treated across all regions, unlike desalination, another solution to water shortages, which is limited to coastal areas and is very energy-intensive.
France lagging behind
In France, reuse remains underdeveloped. The reasons for this are a lack of public awareness and very strict regulations. Within the European Union, the directive of May 21, 1991 specifies that "wastewater shall be reused where appropriate." European countries therefore each have their own regulations on wastewater reuse.
France has defined the qualities required for the reuse of treated wastewater for crop irrigation or green spaces. Industry professionals are campaigning for a relaxation of the law, which places overly strict restrictions on wastewater reuse, primarily for health reasons. The European Commission recently took up this issue and in 2018 issued a proposal for regulations specifically covering agricultural irrigation, with the aim of facilitating the reuse of treated wastewater.
Depending on the local regulatory context, wastewater reuse is therefore developing unevenly around the world.
Some developed countries experiencing severe drought have turned to wastewater reuse in recent decades: the southern United States (California, Florida, Texas, Arizona, for example), Australia, Singapore, Israel, and the Persian Gulf countries. The state of California, a pioneer in wastewater reuse, introduced the first regulations in this area at the beginning of the 20th century. Since then, these regulations have evolved with increasingly advanced treatment methods to guarantee high-quality water, which has inspired many countries.
In Europe, water needs differ between the north and south: wastewater reuse practices are more widespread in southern countries. In some cases, however, such as in Greece and Italy, overly strict regulations are hindering this practice, as they entail excessive costs for monitoring water quality (74 parameters to be monitored according to Greek regulations). In Spain, the most active European country in this field, more than 150 reuse projects have been implemented in recent years.
A delicate assessment
While more than sixty countries worldwide reuse wastewater, 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 produce low-quality water due to insufficient treatment levels.
In terms of the amount of water reused per capita, Qatar, Israel, and Kuwait are the best performers. Kuwait, Israel, and Singapore rank highest when the criterion considered is 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 benchmark
Singapore is a world-renowned case study and a benchmark in this field. Due to its very high population density, this 699km² island has had to cope with increasing water shortages and has turned to reusing wastewater after advanced treatment combining microfiltration, reverse osmosis, and UV radiation.
This water, known as "Newater," is used for industrial applications and in cooling towers, but a portion is also mixed with natural water and fed into the drinking water network. Such examples of direct reuse for drinking water are rare, mainly due to psychological barriers.
The wastewater treatment plant in Windhoek, Namibia, is the only example of direct reuse for large-scale drinking water production (21,000m3/day).
Significant 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 concerns regarding reuse for domestic purposes were health risks (69%) and aversion to this use (44%).
In addition, its use for more or less restrictive purposes, such as irrigation, groundwater recharge, or direct consumption, could be limited due to the quality of the water in question. The main drawbacks of this water are its high salinity, which can harm agricultural productivity and soil quality, and the presence of emerging pollutants, known as "micropollutants," which have been identified as endocrine disruptors.
However, in France and internationally, water treatment research laboratories are actively working on the development of new innovative processes, particularly those based on combination of physical and chemical treatments which will enable water quality suitable for the intended uses to be achieved.
Julie Mendret, Senior Lecturer, HDR, University of Montpellier
This article is republished from The Conversation under a Creative Commons license. Readthe original article.