With nine months of drought, 25% less rain than normal and a record year of heat, 2022 was seen as a wake-up call for the French government.
While in the middle of August, 700 municipalities were affected by water supply problems, some rivers and groundwater were still struggling in December to return to levels close to normal.
"The levels of the groundwater in December are unsatisfactory. The rains infiltrated during the fall are very insufficient to compensate for the deficits accumulated during the year 2022 and to improve the state of the groundwater in the long term", alerted the Bureau of Geological Research and mines (BRGM) in early January, deeming the situation "worrying".
For the organization, the observation is clear: only rainy and cold weather until early spring could now make it possible to replenish sufficient water stocks before summer.
Otherwise, the scenario of the year 2022 could well be repeated in 2023.
To cope, and while this situation is likely to repeat itself anyway due to climate change, the government now wants to anticipate.
On January 25, the Minister for the Ecological Transition, Christophe Béchu, thus unveiled 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 'summer 2022'", says the minister.
Among the axes envisaged: sobriety measures to reduce withdrawals from groundwater, a fight against leaks but also better reuse of wastewater, a practice which consists in directly reusing the water leaving the treatment plant without go through a return to the natural environment.
For Julie Mendret, researcher at the Membranes Institute of the University of Montpellier, who works on the reuse of wastewater, this practice must indeed be generalized for better water management, but must remain used "in the event per case".
France 24: Where is France on the reuse of wastewater?
Julie Mendret:
"France is lagging behind other countries with less than 1% of reused wastewater. In our Spanish neighbours, this figure is 15%. It's 8% in Italy. And in Israel, a pioneering country in this area, is more than 80%.
But the situation has been changing for a few months.
While France mainly uses this technique for agricultural irrigation and the watering of green spaces, in particular golf courses [according to the panorama drawn up in 2017 by Cerema, 60% of cases were intended for irrigation and 26% for golf courses, Editor's note] since March 2022, a decree has also made it possible to explore urban uses such as cleaning roads or fighting fires.
France also hosts a pilot project in Europe, the Jourdain project, located in Vendée.
Its ambition is to make drinking water indirectly, from wastewater: instead of being discharged into the sea, part of the water from the Sables-d'Olonne wastewater treatment plant will be recovered and treated before being reinjected into a water reservoir.
This body of water will then serve as a resource for the nearby drinking water treatment plant.
The drought of 2022 has reinforced the observation that we must now think about new ways of managing our water resources.
And the reuse of wastewater appears today as a solution for the future.
>> To read also: waste water, sea water, rain… in search of new sources against drought
How does wastewater reuse work
?
To understand, we must first remember how the so-called "little water cycle" works.
Usually, fresh water is pumped from our groundwater, treated in so-called potabilization stations, and then used.
Spent, they are collected by treatment plants, treated again and discharged into a natural environment – generally in the sea or rivers.
When we decide to reuse wastewater, we offer it a new use rather than rejecting it.
Depending on usage, they may or may not receive additional processing to ensure they are of good quality.
This will be the case, for example, if you want to use them to water market garden crops, with fruits or vegetables that you may need to eat raw.
Conversely, we could possibly do without it if the water is used in a place that does not receive the public.
However, in some cases, the discharge of wastewater makes it possible to ensure a sufficient flow of waterways... 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.
This is a particularly consistent practice in coastal areas as it gives fresh water a new use instead of being discharged into salty seawater.
In addition, the more we increase the pressure on the water tables in these areas, the more we risk causing saline intrusions [the intrusion of salt water under fresh water], further reducing access to fresh water. .
Recycling fresh water can also be very relevant when it avoids discharging it into sensitive environments.
This is the case in Noirmoutier, in Vendée, for example.
Farmers already use this practice primarily because it helps to preserve nearby shellfish farming ponds.
On the other hand, in the continental zones, it is more complex.
In some rivers, part of the flow comes from the discharge of wastewater from treatment plants.
If the quantity of water is reduced, particularly in a context of drought, this can have consequences on the level of the watercourse and therefore on the ecosystems.
In these cases, the reuse of wastewater is certainly not the preferred solution.
Finally, from a more practical point of view, it is important to clearly determine what use you want to make of the reused water.
The place that will benefit from it must be close to the treatment plant because transporting water generates prohibitive costs.
What are the obstacles that persist in generalizing this practice
?
Social acceptability remains a major issue.
Many misconceptions continue to circulate about wastewater reuse, mostly due to lack of knowledge.
It is essential that the actors continue to communicate on this subject to get rid of misconceptions and educate.
Especially since, as we have mentioned, the water leaving the stations is of good quality and there has never been any case of any contamination with reused treated wastewater.
Regulations can also be a hindrance because they remain quite cumbersome and often require very long procedures.
For project leaders, this can be quite discouraging.
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 still have access to conventional resources that are less expensive than reused water, by drawing from boreholes or river water.
There is therefore an economic logic that encourages them not to favor this technique.
It is also important that we move forward on this issue so that the reuse of water becomes more of an incentive.
In summary, can wastewater reuse be some sort of silver bullet in this anti-drought plan
?
We must at all costs avoid creating a "rebound effect".
Because by generalizing the recycling of wastewater, we could give a 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 reduce the pressure on our groundwater remains to draw less from it.
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