Overshadowed by the events that have hit the region since the death of young Nahel, killed by the shooting of a policeman, the water file in Île-de-France has been trying to resurface for a few days. On June 26, the public authorities responsible for supplying drinking water to Paris, and some of the inhabitants of the Ile-de-France region, called for an urgent “Grenelle de l’eau” for the region. This Friday again, several associations will hold a press conference to demand “citizen, public and resilient water management in Île-de-France”.
The reason for their anger? The Ile-de-France Water Syndicate (Sédif) project consists of equipping its three water treatment plants with membrane technology that promises “pure water”. An enticing promise on paper… But strongly contested. To understand the water war taking shape in the region, 20 minutes review this case.
A new technology that makes it possible to obtain “ultra-pure” water
In the pipeline for several years, the project to transform the three Sédif stations ((Méry-sur-Oise (95), Choisy-le-Roi (94) and Neuilly-sur-Marne (93)) to provide them with technology called “Low Pressure Reverse Osmosis” was relaunched by President André Santini in April.
This technique, already used for desalination, consists of propelling water through membranes whose pores are so small that they would filter out 80 to 99% of the molecules of the new pollutants observed recently. It would also improve the hardness of the water, reducing the limestone content by 2.5 to 3 times and would make it possible to do without chlorine.
Problem, almost all the other actors of the water sector oppose it. And the grievances abound.
An environmental impact and a transfer of pollution to others
First stumbling block, the environmental impact. Dan Lert, president of Eau de Paris, one of the four main authorities organizing water distribution in the region, along with Sédif, Sénéo and Aquavesc, explains to 20 minutes the ecological risks of the project: “The transfer of pollution to other water stakeholders is not taken into account. The concentrates (all the waste from the treatment) will be discharged into the course of the rivers in hyperconcentrated volumes. It will be up to the territories downstream to treat them at the risk of further polluting the resources of these territories. It is a crying lack of solidarity. »
An argument underlined by Julie Mendret, Doctor of environmental process engineering and lecturer at the University of Montpellier: “The Sédif project lacks impact studies on biodiversity and on the water points of downstream basins, where other drinking water treatment plants are located. »
The other “not very green” point of the Sédif project is the energy cost of these new generation factories. OIBP’s technology requires three times more energy (mainly electricity) than current plants to operate. “This is the equivalent of the consumption of a city of 40,000 inhabitants. This goes against the challenges of energy sobriety towards which climate change is leading us,” explains Dan Lert.
Two philosophies clash: heavy artillery versus prevention
To justify this choice, the Sédif argues that it is its sources of bad qualities which oblige it. “97% of our resources are surface water, more vulnerable to pollution than the groundwater that Paris selfishly keeps for itself,” explained André Santini in April. The syndicate also argues that the additional energy expended would be offset by the energy savings that its purer water would bring about by improving the operation of its users’ household appliances.
If the Sédif argues that its watershed represents 12% of French territory, “impossible to control”, to justify the need to bring out heavy artillery, Eau de Paris sees the solution more in prevention and sobriety, and puts in before its new Orly 2 factory inaugurated last week by Anne Hidalgo and which will run on activated carbon.
An effective technology against pesticides or nitrates according to Julie Mendret, but less against new pollutants such as dioxane identified by ANSES in the waters of the region according to a report published last March: “We work with agricultural producers upstream in order to favor better treatment of the land, with fewer pesticides, explains Dan Lert, today 16,000 hectares of the watershed are protected with a clear objective of 20,000 hectares in the short term and 40,000 hectares very sensitive to pollution in coming years. A 47 million euro project for Eau de Paris.
A pharaonic cost and maybe more…
A straw compared to the 860 million euros requested by the OIBP: “If the Sédif invested this money in depollution, can you imagine what we could do? Especially since their factories will not be ready before 2032, in the meantime, the catchment areas and their water continue to be polluted,” comments Dan Lert.
A bill which could also continue to increase according to one of the players in the sector who prefers not to be quoted: “Sedif made its calculations before Covid-19, the war in Ukraine and inflation. 860 million is the starting sum. When consumers will see their bills increase from year to year, they will understand that we will be well over one billion euros, but it will be too late. »
A difference in treatment and treatment
Partner of Sédif as Eau de Paris, Sénéo (water union of the northern half of Hauts-de-Seine) tries to play the appeasement. Regarding the project of the first, Florent Cazy, general manager of Sénéo kicks in touch: “Everyone is lord in his land, and all decisions have been made democratically. However, his vision seems to be similar to that of Eau de Paris: “We rather defend a ”low tech” vision which costs less and is more sustainable. Good quality water requires prevention to achieve purer raw water. To do this, we must invest in the quality of the resource, change agricultural practices and fight against waste. »
Florent Cazy however raises the political question underlying these debates: “Users are assigned to their distributor. They can’t change it like you change electricity suppliers. However, the Sédif project, although more expensive [il devrait augmenter le prix de l’eau pour l’usager d’au moins 30 à 40 centimes par m3] promises ”business class” water, with less taste and reduced hardness. Even if the water from neighboring distributors is excellent, it is not easy to justify to users that it is not as good as next door. This is a question to consider as well. »
Solidarity between territories called into question
But if the political aspect is omnipresent in the mouths of all the actors, what makes this debate so important is that all these networks, although independently managed, are interconnected. Indeed, an agreement between the four major water management authorities in the region promotes solidarity and mutual aid in the event of a crisis. Works, occasional pollution, shortage due to drought, all the networks are connected and the factories are working at undercapacity to be able to remedy the defect of one or more of them. A crisis simulation exercise carried out last September also showed that this solidarity was working.
However, according to Eau de Paris and Sénéo, the “new premium water” from Sédif could undermine this system. Indeed, no study has been carried out to show that this water, very low in chlorine, would be suitable for the networks of other organisations. “Sedif assumes that its network is good enough to prevent bacterial proliferation with its ultrapure water. But we lack information and we do not know how these networks would react with different chlorinated waters. »
“In a case of crisis, we refer to the prefect who makes the decisions. But we need a uniform framework to respect our priority, which is to secure the water resource of all Ile-de-France residents,” concludes Florent Cazy. This is precisely what Eau de Paris did by requesting the intervention of the regional prefect to define a collective strategy.