The timing is about. On April 6, the National Agency for Food, Environmental and Occupational Health Safety announced that it had detected metabolite levels of chlorothalonil, a pesticide banned since 2020, above the regulatory threshold in a water sample. drinkable out of two during his last national campaign.
Two weeks later, the Syndicat des Eaux d’Ile-de-France (Sedif) is launching, this Thursday, April 20, a major public consultation on drinking water in Île-de-France. If this consultation has been planned since 2022, the concordance of the two events is timely for the organizers.
Surface water more polluted than groundwater
“ANSES’ results reinforce our desire to improve water quality in Île-de-France,” commented André Santini, Mayor of Issy-Les-Moulineaux (92) and President of Sedif. Because that is the subject of this consultation. The syndicate would like to launch the transformation of its three drinking water treatment plants in Île-de-France: Méry-sur-Oise (95), Choisy-le-Roi (94) and Neuilly-sur-Marne (93) in order to to equip them with the latest technologies in this area.
The 135 municipalities that cover the territory of Sedif can only drink with “surface” water, from the Seine, the Marne and the Oise. Water from watersheds, more likely to transport pesticides from agriculture, drug residues, endocrine disruptors and micropollutants, than water from groundwater.
“The drinking water supplied by Sedif to its four million users is today of excellent quality according to current criteria despite the poor quality raw material that our resources allow us, very vulnerable, welcomes the former minister. , but the measurements indicate that the three current plants cannot retain some of the new pollutants, such as the recently discovered pesticides and eternal pollutants. »
A new technology capable of filtering pesticide particles
To do this, the union wants to transform its factories to equip them with new technology from the membrane industry. Finally, not entirely new since it is already this technology that has equipped the Méry-sur-Oise site since 1999. “The water is filtered through rollers made up of 28 membranes whose pores have a diameter less than one billionth of a meter is up to 100,000 times thinner than a hair,” explains Sylvie Thibert, water quality and health risk management engineer. These membranes thus trap unwanted particles. This is the so-called “nanofiltration” technique.
State-of-the-art technology which ensures the supply of drinking water to 800,000 people and which is of interest abroad: “We regularly receive European and Asian visitors who are interested in this technology”, confirms Adrien Richet, high performance sector engineer, in charge of the Méry-sur-Oise plant.
But these membranes have a life expectancy of seven years and the last ones used expire in 2025. However, the membrane sector has succeeded in improving this principle thanks to the technique of low pressure reverse osmosis (LOBP). Without going into a tedious, but interesting, development, it is the same technique but the pores of the membranes are even smaller (up to a thousand times finer) and would make it possible to filter 80 to 99% of the molecules of the new pollutants observed recently, including chlorothalonil.
Less limestone for household appliances, less “chlorinated” taste for the user
But not only. In addition to improving water quality, OIBP would also improve water hardness, by reducing the lime content by 2.5 to 3 times and would limit the use of chlorine to a tiny amount. , imposed by the Regional Health Agency (ARS), as a preventive measure (Total elimination of traces of organic matter and viruses).
Not insignificant advantages on the lifespan of household appliances and a significant improvement in the taste of water according to the members of Sedif. “We helped out our friends from Cergy-Pontoise during recent work on their own network and since then the inhabitants have asked to find our water, believing that it tastes better”, boasts Pierre-Edouard Éon, Mayor of Méry-sur. -Oise and vice-president of Sedif.
If the Val-d’Oise factory has no choice but to switch to superior technology, the current one no longer being offered by manufacturers, the union would like to take the opportunity to transform the other two factories, Choisy-le-Roi and Neuilly-sur-Marne which still use the conventional channel. Improvements that would coincide with the new delegation contract, currently with Veolia, which is due to start in 2025 for a period of 12 years.
A salty note…
Of course, this technological gap has a cost, and not the least. According to Sedif, the total bill would amount to 870 million euros. The bulk of the note would be dedicated to the construction of new factories in Choisy-le-Roi (about 377 million euros) and Neuilly-sur-Marne (373 million euros). The remaining ten million would be used to change membranes at the Méry-sur-Oise plant.
This is one of the main reasons for this consultation, under the aegis of the National Commission for Public Debate (CNDP). If the primary objective put forward by Sedif is to inform the population of these transformations and to respond to questions and concerns, the union also concedes that consultation is imposed: “The CNDP imposes a public debate for any industrial equipment project of an amount greater than 300 million euros “, explains André Santini. Anyway, this consultation does not include a binding aspect “as was the case for scooters in Paris”, specifies the elected official.
…but compensated
According to Sedif, the amount invested would be advanced by the new concessionaire and amortized over the next forty years and of course passed on to users’ bills: “It would be an increase of 30 to 40 centimes per m3, i.e. between 3 and 4 euros monthly per household”, advances Luc Strehaiano, Mayor of Soisy-sous-Montmorency (95) and vice-president of the union.
An additional cost for the French, already affected by inflation, but which will quickly be compensated according to Sedif which advances the figures of the IEIC firm of a saving of 124.6 euros on average per household due to savings made in consumption of electricity. energy and lifespan, purchase of cleaning products, bottles of water and softener.
All work should start in 2027. While it will only take a few weeks for the Méry-sur-Oise plant to replace its membranes, the other two plants should be completed and commissioned between 2030 and 2032.