Upgrading constructed wetlands using upstream (advanced) oxidation technology to improve the removal of micropollutants and reduce the ecotoxicological risks.

This study shows research pathways from the Interreg-EmiSûre project, where several admixtures were studied as substrates for constructed wetlands (CWs), to the Interreg-CoMinGreat project, which proposed a pre-oxidation step to improve the removal of micropollutants, extend CW lifetime, and reduce the surface area. In EmiSûre, CWs (15% of activated carbon and 85% of sand) were installed in Echternach wastewater treatment plant (WWTP) (Luxembourg) achieving 80% removal of most the target compounds. Then, the configuration of these CWs was combined with photo-Fenton in Bliesen WWTP (Germany) at a natural pH; dosing 1.5 mg L-1 of iron (Fe3+) (citric acid as the chelating agent); and 20 mg L-1 of H2O2. Also, UV/H2O2 treatment was tested to avoid iron dosage. Diclofenac present in the treated effluent of Bliesen is a key pollutant that poses medium ecotoxicological risks for aquatic life. Its removal in CWs reaches 88%, however, it is known to be very restrictive during the adsorption process. With the pre-oxidation, 52% of diclofenac is removed, resulting in a lower load to be treated by the CWs; therefore, reducing considerably the required surface area. Implementing UV/H2O2 treatment as the first step could reduce the CW surface area per PE to 0.19 m2.