Incidence des pratiques d’entretien des toitures sur la qualité des eaux de ruissellement : cas des traitements par produits biocides

Abstract : Firstly, this thesis listed the different roof treatment practices in France. Once the major treatment practice selected (biocidal treament), the analytical protocol of the most widely used molecule (benzalkonium or alkyldimethylbenzylammonium) was developed. This protocol has been followed to evaluate the biocide concentration levels in roof runoff after a treatment. A double approach was considered : - Follow up of the benzalkonium flux for one year in runoff using 12 bench tests exposed to natural conditions. - Evaluation of the influence of different parameters (material, product dosage and rain intensity) on benzalkonium emmission processes with simulated rains. Finally, all the data acquired allowed the evaluation of the incidence of biocidal treatments on roof runoff contamination at different scales ( local and residential watershed). The results of the bench tests showed a very high benzalkonium contamination during the millimetres of rain (5 to 27 mg/L), higher than the different EC50s of aquatic organisms ( 5.9 ùg/L). Furthermore, the results showed an influence of the tile material on the release of benzalkonium : clay tiles were less washed off than concrete tiles. The contamination decreased with successive rains, but remained significantly high several months after treatment. Moreover, laboratory studies showed a proportional release of benzalkonium from waterproofed tiles with respect to the biocidal mass spread. On the contrary, tiles without any surface treatment were not sensitive to the product's dosage. On a local scale, precautions have to be taken during treatment with respect to the harvest / reuse of the runoff. Indeed, high benzalkonium concentrations during the first rains may have a potential impact on watered plants, microbial equilibrium in the collection tank and irritating effects on human. A deconnection of the tank for at least three to five months will reduce the risks. Finally, based upon the bench tests results and a survey on roof treatment practices, the benzalkonium concentrations and fluxes were injected in a mathematical model on a watershed scale. The results showed a significant contamination linked to the particles. The annual mass of benzalkonium transferred to the rainwaters could reach 0.85kg / waterproofed ha / year
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Antoine van de Voorde. Incidence des pratiques d’entretien des toitures sur la qualité des eaux de ruissellement : cas des traitements par produits biocides. Sciences de la Terre. Université Paris-Est, 2012. Français. ⟨NNT : 2012PEST1035⟩. ⟨pastel-00730831⟩

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