When he sits down to his table on summer evenings for an aperitif, this Toulousain sometimes smells of rotten eggs in his nose, other days it looks more like fermented cabbage, a chosen one is sure it smells rarely the rose on the side of Ginestous. For years, the
wastewater treatment plant which treats the vast majority of wastewater in the Toulouse metropolis is singled out for
bad smells who produces it.
?? # EauDeToulouseMetropole recruit a Nose Jury 👃: volunteer citizens who will be trained in odor recognition, in order to be able to identify and report them in real time 📲 pic.twitter.com/hDULbOgOZ5
– Cecilia Cazaban (@CeciliaCazaban) 20 October 2021
In an attempt to reduce these odor nuisances, Asteo, a subsidiary of Suez which manages these 20 hectares installed on the edge of the ring road on behalf of Toulouse Métropole, has embarked on a vast odor reduction plan for an amount of 10 million euros. euros and which is due for completion next year. This involves covering certain structures or setting up a deodorization system in others.
Two training evenings
But the scents have not yet disappeared and these bouquets, far from being flowery, still regularly titillate the nostrils of the locals. To better identify them, and complete the existing sensors of molecules concentrated in the air, a jury of residents’ noses has just been set up. “Every day I cycle past the station to go to work and I regularly smell a very strong odor”, explains a young man, present during one of the two evenings on the stage. Last Wednesday and Thursday, for three hours, about twenty volunteers learned what certain fragrances of the different treatment processes correspond to.
“An odor is an indicator of malfunction. It can be rancid, acrid, garlic, pungent or even foul. Under anaerobic conditions, that is to say without oxygen, we will have unpleasant odors. Acetic acid smells like vinegar, hydrogen sulphide has a typical rotten egg smell, it’s a problematic compound. Methyl mercaptan will give off a cabbage odor ”, detail Caroline Bouchet, engineer at Suez, one of the two specialists of the company responsible for providing indicators or future human detectors.
A round of smells
There is no question for local residents to learn the catalog of all gas products on site. To help them determine what they smell from day to day, a round of scents has been developed to “define a common language”.
And it is far from easy. To test these noses, sticks of various odors were circulated between the volunteers. For one of them it smelled like chlorine, when others had difficulty defining. And surprise in the assembly when the formators revealed that it was about “scents” of fecal matter.
When they smell nuisance, each of the residents presents to declare on a dedicated site what it makes them think, whether it is popcorn, solvent or fermented vegetables. “Our agents are also trained, but they are not always present at the moment T, certain odors are carried by the wind too. These feedbacks will enable us to identify the problems and improve operations, ”insists Loïc Depoutre,“ Domaine Usines ”manager within the Toulouse Métropole water purification service.
To help the nostrils to soak up the different molecules that emanate from the facilities, nothing better than a walking tour to complete this training. Between two installations, the participants stop with their noses in the air. One of them exclaims, “ah, that smell we often have”. A breeze carrying strong scents, between urine and rotten fish, then surrounds the small group. Rate. “This is the green waste compost bin, which is right next door, it does not come from the station,” says one of the Ginestous agents.