Wastewater reuse: Which countries are leading the way?
In the face of a global water shortage, wastewater reuse is a promising solution for the future.
Julie Mendret, University of Montpellier
Once treated, wastewater can indeed be used for a variety of purposes: irrigating green spaces or crops, firefighting, street cleaning, or 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 percent of their water needs through the reuse of treated wastewater.
The ubiquity of wastewater makes it feasible to treat it across all regions, unlike desalination—another solution for addressing water shortages—which is limited to coastal areas and is highly energy-intensive.
France is lagging behind
In France, “reuse” remains underdeveloped. The reasons for this include a lack of public awareness and very strict regulations. Within the European Union, the directive of May 21, 1991, states that “wastewater shall be reused where appropriate.” European countries therefore each have their own regulations governing the reuse of wastewater.
France has thus established the required standards for the reuse of treated wastewater for the irrigation of crops or green spaces. Industry professionals are advocating for a relaxation of the law, which imposes overly strict regulations on wastewater reuse, primarily for health reasons. The European Commission recently took up this issue and issued a proposal in 2018 for regulations specifically addressing agricultural irrigation, with the aim of facilitating the reuse of treated wastewater.
Depending on local regulatory frameworks, the reuse of wastewater is therefore developing at varying rates around the world.
Over the past few decades, certain developed countries facing severe drought have turned to wastewater reuse: the southern United States (California, Florida, Texas, and Arizona, for example), Australia, Singapore, Israel, and the Persian Gulf countries. The state of California, a pioneer in wastewater reuse, enacted 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 ensure high-quality water, serving as a model for many countries.
In Europe, water needs differ between the north and the south: wastewater reuse practices are thus more widespread in southern countries. In some cases, however, such as in Greece and Italy, overly strict regulations hinder this practice, as they result in excessively high costs for monitoring water quality (74 parameters to be monitored under Greek regulations). In Spain, the European country most active 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 when considering annual volumes, China, Mexico, and the United States are the countries that reuse the largest quantities; however, the first two produce water of poor quality due to inadequate treatment.
In terms of the amount of water reused per capita, Qatar, Israel, and Kuwait rank highest. Kuwait, Israel, and Singapore rank highest when the criterion is the percentage of reused water relative to total water use. Finally, when it comes to technological advancements, California, Singapore, and Japan are likely the most innovative countries.
The Singapore Model
Singapore is a world-renowned leader in this field. Due to its extremely high population density, this699-square-kilometer island has faced increasing water shortages and has turned to the reuse of treated wastewater using state-of-the-art technology that combines microfiltration, reverse osmosis, and UV disinfection.
This water, known as “Newater,” is used for industrial applications and in cooling towers, but a portion of it is also mixed with natural water and supplied to the drinking water system. Such examples of direct reuse for drinking water production are rare, mainly due to psychological barriers.
The wastewater treatment plant in Windhoek, Namibia, is thus 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 faces a problem of social acceptance: a recent survey in Kuwait showed that the two main concerns regarding the reuse of wastewater for domestic purposes were health risks (69%) and a distaste for this practice (44%).
Furthermore, its use for various purposes—such as irrigation, groundwater recharge, or direct consumption—may be limited due to the quality of the water in question. Indeed, the major drawbacks of this water are its high salinity, which can harm agricultural productivity and soil quality; there is also the presence of emerging pollutants, known as “micropollutants,” identified as endocrine disruptors.
However, both in France and internationally, water treatment research laboratories are actively working to develop new innovative processes, particularly those based on combination of physical and chemical treatments that will ensure water quality suitable for the intended uses.
Julie Mendret, Associate Professor, HDR, University of Montpellier
This article is republished from The Conversation under a Creative Commons license. Readthe original article.