This paper investigates the treatment of stormwater pollution within a wastewater treatment plant (WWTP) located near Paris, France. Under dry-weather flows (DWF), its treatment consists in a physico-chemical lamella settler and a 3-stage submerged trickling filter. Under wet-weather flows (WWF), the biological treatment is modified to treat 3-times higher flows: 30% of the influent is treated on one stage only, while 70% is treated through two stages. In this work, we studied concentrations and removal of wastewater quality parameters, alkylphenols (APs) and polybromodiphenylethers (PBDEs) within the WWTP during DWF and WWF. 5 campaigns were performed during DWF and 4 rain events were sampled. Dissolved and particulate phases of APs and PBDEs were analyzed separately. In raw effluent, AP and PBDE concentrations are 1.5 to 5 fold higher under WWF. In the settler, an important proportion of the particulate phase of APs (>84%) and PBDEs (>87%) is eliminated. The biological treatment enhances the removal of these pollutants, for both dissolved (especially for APs) and particulate phases (>60%). Except for nitrates and BDE-209, the modified biological treatment seems to have no influence on the treatment of wastewater quality parameters, APs and PBDEs