Reusing wastewater, a good solution to save water?

Reusing wastewater, a good solution to save water?

In France, many departments facing drought are currently facing restrictions on water use. And the situations of tension multiply, evidenced by the degradation of large reserves – “basins” – in Vendée recently.

At European level, the situation is similar. “It is our duty to stop wasting water and use this resource more efficiently,” warned EU Environment Commissioner Virginijus Sinkevicius on August 3, issuing advice to member states on how to better reuse water in the agricultural sector. Among its priorities: reuse of treated wastewater (Reut or reuse in English).

1. What is it?

Wastewater is intended to be discharged after industrial or domestic use which has caused it to lose its initial purity. To eliminate undesirable chemical and biological contaminants, they are treated in a wastewater treatment plant, before being generally discharged into the natural environment.

However, they could be reused for four different uses, which would save drinking water, notes the Water Information Center: agricultural irrigationuse by communities, cleaning for industries and recharging of groundwater, which represents the main reservoir of drinking water.

2. Which countries are at the forefront?

Currently, the treated wastewater reuse market is mainly driven globally by Asia – particularly China – as well as the United States for industrial use, and the Middle East for industrial use. irrigation, according to Yvan Poussade, international manager of this subject at Veolia, a French water and waste management giant. Israel already reuses 90% of them.

In Europe, it was the countries around the Mediterranean, confronted before France with situations of pronounced water stress and significant agricultural needs, which had taken the lead. Cyprus re-employs them at 20%, Spain 14%, Italy 8%.

In 2020, the European Union (EU) adopted a regulation, in force from June 2023, aimed at facilitating the Reut, in particular for agricultural irrigation (excluding green spaces), while harmonizing the rules applicable in all Member States. Because according to the European Commission, more than 40 billion m³ of wastewater are treated each year in the EU, but only 964 million m³ are reused.

3. Where is France?

Since the initiative carried out on the island of Noirmoutier (Vendée), several experimental projects have been launched across France. Watered green spaces in Sainte-Maxime (Var) via a drip fed by this treated wastewater, to its reuse for cleaning urban sewerage pipes in Deauville (Calvados), passing through the Disneyland Paris park. Including with manufacturers, such as Cooperl, which recycles a large part of it in its Breton slaughterhouses.

But France is late : less than 1% of the water that leaves its 22,000 treatment plants is reused, within the framework of initiatives still mainly allocated to agricultural irrigation and the watering of golf courses, and often intended for seasonal use. The regulations in place since 2010, reviewed in 2014, regulate reprocessing and reuse, in order to protect the population in terms of health and the environment. Even if the industrialists of the sector judge it ” drastic “ compared to that of European neighbours.

“For two years, we have seen the arrival of many municipalities wanting to set up Reut solutions on their territory, but they do not necessarily realize the time required to put together this type of file, for which authorization requests take several months. even years to succeed in France”, assures Yvan Poussade. The European framework should allow harmonisation.

4. What do the regulations say?

French regulations determine four levels of sanitary quality of treated water, depending on the uses: A (for irrigation of market garden crops, pastures, green spaces open to the public), B, C (for irrigation of copses) and D. “All coastal towns that have resource or drought problems should look into this solution for everything that is not drinking water, believes Yvan Poussade. But the projects should not be done to the detriment of the environment, of the waterways in the summer period. »

In 2019, the Assises de l’Eau aimed to triple the volumes of unconventional water reused by 2025. In March 2022, the government authorized, in the wake of the anti-waste law for a circular economy, “on an experimental basis of new uses of treated wastewater, previously prohibited, in particular for urban uses” : road washing, hydrocleaning of networks, but also groundwater recharge.

The Jourdain demonstration project could also constitute “a first in Europe”, according to its promoters: inspired by countries plagued by water shortages such as Namibia, it will make it possible in the coming years to secure the supply of drinking water to Vendée residents thanks to a refining unit under construction in Les Sables-d ‘Olonne.

Read also : Changing wastewater into drinking water: a first in Europe in Les Sables-d’Olonne

5. What are the brakes?

The current brakes are of several orders. Financial of course. Because to be reallocated, the treated wastewater must undergo additional treatments, and will therefore be more expensive depending on the quality required for its end use. This requires dedicated infrastructure, not to mention the cost of new pipes. A large part of infrastructure funding can be supported by European or local grants. There remain heavy operating costs.

“Compared to a withdrawal from the natural environment on which farmers and irrigators pay a fee of the order of 1 to 3 centimes per m3then have transportation and pumping costs to their irrigation system, one is potentially times five on the costs of a Reut solution” , recognizes Yvan Poussade. He thinks he “we must not think in terms of financial benefits but of the sustainability of the activity”.

The key to success lies in the collective, if we are to believe a study by Onema and Irstea, carried out in 2014, relating to French projects generating strong economic profitability for communities. All combine geographical proximity to the treatment plant and potential major users, the existence of links between the providers of Reut’s services and the users, and a long reflection beforehand.

It is also necessary to respond to the concerns of the population about these “grey waters”. French players in the sector have “technical mastery and highly developed sanitary water management procedures, and everything needed to guarantee that this risk is controlled: it is no more risky on arrival than other types of water for the uses that are considered » , assures Yvan Poussade.

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