Résumé
Xenobiotics, such as some pharmaceuticals and pesticides, are poorly treated in wastewater treatment plants (WWTPs). Thus, their occurrence into the aquatic environment is more and more highlighted. Adsorption process on materials, such as in tertiary stage of treatment, could be a solution to decrease the concentrations of xenobiotics in effluents that are discharged into the aquatic environment. We carried out an original experiment involving treated domestic wastewater spiked with a cocktail of 10 xenobiotics known as being poorly eliminated in WWTPs (8 pharmaceuticals and 2 pesticides). Two mineral adsorbent materials (expanded clay and zeolite), representing a possible alternative to activated carbon, were evaluated for the adsorption of the cocktail of xenobiotics. We studied the influence of the concentration level of xenobiotics on adsorption results. We focused on the concentrations near from usual effluent ranges to be representative with conditions faced in tertiary treatment stage. If activated carbon was the most efficient adsorbent material, both alternative adsorbent materials showed good adsorption efficiencies for the 10 xenobiotics (in the range of 50-100% depending on the couple adsorbent material / xenobiotic). Kd partition coefficients were quantified for different xenobiotics concentration ranges. At low concentration (0.1 – 10 µg/L), expanded clay showed higher Kd values than at high concentration (100 – 1000 µg/L) for a majority of xenobiotics (7 among 10). Kd values for zeolite seemed to be independent of xenobiotic concentration levels. Our results point out that mineral microporous adsorbent are credible alternatives to activated carbon for adsorption of xenobiotics usually known to be poorly eliminated in WWTPs. The results suggest a possible use into a tertiary stage of treatment in wastewater treatment plants.