The French government on Wednesday listed a series of measures to deal with droughts, which are becoming more frequent due to climate change. Among the proposed measures is the democratization of the reuse of wastewater for irrigation or irrigation. This technique is still lagging behind in France, despite a new push in recent months.
With nine months of drought, 25% less rain than normal and a record hot year, 2022 was seen as a wake-up call for the French government. While 700 municipalities were affected by water supply problems in mid-August, some rivers and groundwater tables were still struggling in December to return to levels close to normal.
“The groundwater levels in December were unsatisfactory. The infiltrated precipitations during the autumn are very insufficient to compensate the deficits accumulated during the year 2022 and improve the state of groundwater in the long term,” he warned at the beginning of January the Bureau of Geological and Mining Research (BRGM), which considered the situation “worrying”. For the organization, the verification is clear: only rainy and cold weather until the beginning of spring could make it possible to replenish sufficient water reserves before summer. Otherwise, the 2022 scenario could well be repeated in 2023.
To deal with this situation, which will probably repeat itself in any case due to climate change, the Government now wants to anticipate. On January 25, the Minister for Ecological Transition, Christophe Béchu, revealed in the newspaper ‘Le Parisien‘ the outlines of a “national water plan” intended to completely review the water management strategy in France. “There will be a before and after the summer of 2022,” said the minister.
Among the areas planned are sobriety measures to reduce the extraction of groundwater, the fight against leaks and better reuse of wastewater, a practice that consists of reusing water directly from a treatment plant without returning it to the natural environment.
For Julie Mendret, a researcher at the Membrane Institute of the University of Montpellier, who works on the reuse of wastewater, this practice must be generalized for better water management, but it must remain “case by case”.
France 24: What does France think about the reuse of wastewater?
Julie Mendret: “France lags behind other countries, with less than 1% of wastewater reused. In Spain, the figure is 15%. In Italy it is 8%. And in Israel, a pioneer in this field, it exceeds 80%.
But the situation has changed in recent months. Although France has mainly used this technique for agricultural irrigation and irrigation of green spaces, especially golf courses (according to the balance prepared in 2017 by Cerema60% of the cases were for irrigation and 26% for golf courses, editor’s note) since March 2022, a decree allows exploring urban uses as well, such as road cleaning or firefighting.
France is also hosting a pilot project in Europe, the Jourdain project, located in the Vendee. Instead of being discharged into the sea, part of the water from the Sables-d’Olonne treatment plant will be recovered and treated before being reinjected into a reservoir. This body of water will then serve as a resource for the nearby drinking water treatment plant.
The 2022 drought has reinforced the fact that we must now think about new ways to manage our water resources. And the reuse of wastewater now seems to be a solution for the future.
How does wastewater reuse work?
To understand it, we must first remember how the so-called “little water cycle” works. Fresh water is normally pumped from our groundwater, treated in so-called water treatment plants and then used. Once used, it is collected by treatment plants, treated again and discharged into a natural environment, normally the sea or rivers.
When it is decided to reuse wastewater, it is given a new use instead of being dumped. Depending on its use, it may or may not receive additional treatment to ensure its quality. This will be the case, for example, if it is going to be used to irrigate gardens with fruits or vegetables that can be eaten raw. On the other hand, it may not be necessary if the water is used in a place little frequented by the public.
However, the discharge of wastewater guarantees in some cases a sufficient flow in the rivers… Should this practice be generalized throughout France?
No, it is essential to act on a case-by-case basis because the reuse of wastewater is not relevant everywhere. It is a particularly consistent practice in coastal areas because it puts fresh water to new use instead of dumping it into salty seawater. Additionally, the more pressure is placed on groundwater in these areas, the more likely saline intrusion (the intrusion of saltwater under freshwater) will occur, further reducing access to freshwater.
The recycling of fresh water can also be very relevant when it is avoided to discharge it in sensitive environments. This is the case of Noirmoutier, in the Vendée, for example. Farmers already use this practice mainly because it preserves nearby shellfish ponds.
In continental areas, however, it is more complex. In some rivers, part of the flow comes from the discharge of wastewater from treatment plants. If the amount of water is reduced, especially in case of drought, this can have consequences for the level of the water course and, therefore, for the ecosystems. In these cases, the reuse of wastewater is, of course, not the preferred solution.
Finally, from a more practical point of view, it is important to determine what use is to be given to the reused water. The place that will benefit from it must be close to the treatment plant, since transporting the water is too expensive.
What are the obstacles that still prevent the generalization of this practice?
Social acceptance remains a major issue. There are still many misconceptions about the reuse of wastewater, mostly due to a lack of knowledge. It is essential that stakeholders continue to communicate on this topic to dispel misconceptions and educate. Above all because, as we have mentioned, the water that comes out of the plants is of good quality and there has never been any case of contamination with reused purified wastewater.
Regulations can also be an obstacle because it is still quite heavy and requires often very long procedures. For project managers this can be quite daunting. But despite everything, having this clear regulatory framework is necessary: it is the guarantee that the practice is supervised and safe, especially for our health.
Finally, unlike other countries, French farmers continue to have access to conventional resources that are cheaper than reused water, using boreholes or river water. Therefore, there is an economic logic that encourages them not to favor this technique. It is also important that we make progress on this issue to make water reuse more attractive.
In short, can wastewater reuse be some kind of silver bullet in this drought plan?
We must avoid at all costs creating a “rebound effect”. Because by generalizing the recycling of wastewater, we could give the false impression of a new abundance of water resources. Obviously, this is not the case. It is really necessary to combine the democratization of these new uses of treated wastewater with sobriety measures. The main solution to relieve the pressure on our groundwater tables is to extract less water from them.
*Interview adapted from its original in French
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