In Chartres and Villefranche-sur-Saône, small invertebrates track down micropollutants

Between 100,000 and 200,000 micropollutants are potentially detectable at the step exit. With ToxMate, Chartres Métropole and the textile printer TIL have undertaken to find out more about the presence of these molecules in their water discharges.

Plasticizers, drugs, detergents, hydrocarbons, metals, pesticides, cosmetics… The list of products containing micropollutants, these undesirable chemical substances observable at very low concentrations, of the order of micrograms, or even nanograms per litre, is endless. However, even at these very low levels, micropollutants can have negative effects on living organisms due to their toxicity, persistence and bioaccumulation.

To win a fight, says the adage, you have to know your enemy: in order to acquire knowledge about these micropollutants, and to initiate any control and/or control actions, when nothing forces you to do so day in the regulations, Chartres Métropole has equipped the Mare Corbonne wastewater treatment plant (step) with the ToxMate biomonitoring tool. This has been marketed since the end of 2021 by ViewPoint, a specialist in automatic monitoring and analysis of animal behavior, which co-developed it with the ecotoxicology laboratory of INRAE ​​in Lyon.

It is a new and continuous vision, more representative

Alexandre Decamps, ViewPoint

The principle is simple: at the exit of the step, a flow of water is continuously diverted and brought into contact with aquatic invertebrates which, in the presence of micropollutants, come out of the state of lethargy in which they have been conditioned (diapause) , and reflexively show signs of restlessness and/or flight behavior. There are gammarus (small freshwater prawns), leeches and Radix (pulmonate gastropods), three very different and complementary groups which currently constitute the best tools for assessing the overall quality of water discharged into the environment.

These sentinels – 16 individuals for each of the three species – are filmed continuously: on the Mare Corbonne site, from where 17,000 m³ of water are discharged daily in the Eure, traffic lights are updated every two minutes. “It is a new and continuous vision, more representative” which is being put in place, rejoices Alexandre Decamps, environment market director at ViewPoint.

The ToxMate biomonitoring station entered service in Mainvilliers, near Chartres, in January 2022, as part of a sixteen-month experiment. For ViewPoint, this is an opportunity to carry out a global study, with continuous measurements which should make it possible to determine whether micropollutants appear at regular frequencies, or on the contrary in a totally random way, for example during a control problem. from the step.

“The better we know, the better we master”

Sanitation plant manager within Chartres Métropole, Julien Pelleray, notes that“a background noise is already perceptible, with micropollutants permanently present (…). From time to time, there are pollution peaks, either for all three organisms at the same time, or just for one”. Water samples are then taken, and measurements relating to around a hundred parameters are carried out in an attempt to identify the micropollutant(s) at the origin of the alert. “We are now in a phase of seeking knowledge”summarizes Julien Pelleray, because “the better we know, the better we master”. Vice-president of Chartres Métropole in charge of drinking water and sanitation, Alain Bellamy remarks that it will be necessary “still time to better analyze” the data collected.

A device of the same type has been installed near Villefranche-sur-Saône, at TIL (Deveaux group), which has been purifying its wastewater in its own step since 2019 – the company treats the water and chemicals used for its activity there. printing and dyeing (soda, hydrochloric acid, dyes, etc.), and discharges into the Saône 30 to 35 m³ of water per hour on average over the year, 7 days a week, 24 hours a day.

Initially, it was the company ViewPoint biosurveillance de l’eau, based in Civrieux, in Ain, which called on the specialist in textile printing and finishing to “neighbor” it to test its solution free of charge. . For two years, the prototype evolves and the pilots are changed several times – it is necessary in particular to adapt the biology to the nature of the releases of TIL, and to perfect the “box”. At the beginning of 2022, the company TIL decided, at the end of the experiment made possible thanks to the Rhône-Mediterranean-Corsica water agency, to invest in ToxMate technology.

Between November 2021 and November 2022, three alerts occurred, mainly on weekends, on half-hour episodes. In none of them, the company found the pollution at the origin of these anomalies. Hence its decision to acquire from the German group Endress+Hauser a sampler who, in the event of an alert, will collect a sample of water for analysis before research, then correction of any malfunction in the plant.

” Nowadaysexplains Jean-Michel Bertrand, director of the TIL plant, we have not yet been in a situation where we would have had to stop discharges into the environment. » He nevertheless assures that the company would do so in the event of an alert lasting more than half an hour.

Article published on December 08, 2022