Removal of refractory micropollutants by a full-scale ozonation
Résumé
Dissemination of chemical substances in the environment is becoming a major issue and wastewater effluents are one of the main point sources. The goal of the present work was to determine the performances on micropollutants removal of a recently developed process consisting in ozone contactor followed by a post-denitrification submerged biofilter. A full-scale tertiary treatment line (600 m3/h) built at Sophia-Antipolis WWTP was studied under various operating conditions (ozone and methanol dosage). The groups of micropollutants monitored include pharmaceuticals, hormones, pesticides (domestic uses) and also compounds listed in the WFD such as metals, phthalates (DEHP) and alkylphenols. Presented results show that with an ozone dosage of 5 g/m3, the tertiary treatment was able to eliminate pharmaceutical compounds, such as antibiotics and betablockers, achieving removal efficiencies higher than 70%. Regarding pesticides, only diuron and AMPA were quantified in the influent of the tertiary treatment, and both were very highlyremoved by the tertiary treatment (60 and 80%). For the majority of the studied substances, major removals were observed at the ozonation stage. This study also permits to highlight the positive effect of this tertiary treatment (especially the ozonation stage) for the removal of recalcitrant micropollutants, i.e. remaining in the effluent after physical and biological treatments.