Nature-based solution as an efficient wastewater pretreatment to enhance micropollutants abatement by solar photo-Fenton at natural pH

This study investigated an innovative and low-cost hybrid system that couples constructed wetland (CW) and solar photo-Fenton (SPF) to enhance the elimination of 17 different micropollutants (MPs) from urban wastewater. The CW unit explored two aquatic plants (Phragmites australis and Cyperus haspan) and two operational modes (with and without recirculation), resulting in four different microcosms. Photo-Fenton experiments were carried out in a bench solar simulator at natural pH using the commercial fertilizer DTPA as iron catalysts. The results showed that the constructed wetlands with recirculation obtained better MPs eliminations than microcosms without recirculation, with no significant difference between the two plants. The average removal of total MPs and different cycles was 67% and 41% in the unit planted with C. haspan, with recirculation and no recirculation, respectively. Additionally, the removal performance of total suspended solids (TSS) and dissolved organic carbon (DOC) from water was also high, reaching about 80% and 50% for TSS and DOC, respectively in the recirculation unit with no increase in nitrites content. The CWs performance resulted in a rise yields of overall MPs abatement in photo-Fenton process, from an average removal of 73% for the single process up to almost complete removal (95%) for the hybrid system. CW with recirculation combined with SPF would let to achieve the corresponding limits according the final use/fate of the effluent in a more economical, sustainable and green way.